Color is a fundamental part of how we perceive and interact with the world around us. The colors we see are a result of how light is reflected off objects and interpreted by our eyes and brains. There are several ways to represent and quantify colors numerically so that they can be reproduced digitally on screens or in print. Two of the most common color models are RGB (red, green, blue) and RYB (red, yellow, blue). Understanding the difference between these models helps explain why colors can appear different on different devices or with different types of inks and paints.
What is the RGB color model?
The RGB color model is based on the three primary colors of light: red, green, and blue. This is an additive color model, meaning the primary colors are combined in varying intensities to create all the other colors we see. Computer and TV screens use the RGB model to produce colors by emitting different levels of intensity of red, green, and blue light.
RGB colors are specified using three values between 0-255 that correspond to the intensity of each primary color. For example:
| Color | Red Value | Green Value | Blue Value |
| White | 255 | 255 | 255 |
| Black | 0 | 0 | 0 |
| Red | 255 | 0 | 0 |
| Lime green | 0 | 255 | 0 |
| Blue | 0 | 0 | 255 |
When red, green, and blue light are combined at full intensity, the result is white light. As the intensity of one or more light colors decreases, darker colors are produced. An absence of all three colors produces black.
Some key advantages of the RGB model:
– It aligns with how computer and TV displays produce color using pixels. This makes it easy to store and display digital images and graphics using RGB values.
– The three primary colors can be combined to produce a wide range of colors visible to the human eye. Although not all colors can be represented precisely.
– RGB colors are device-independent. An RGB value represents a specific color regardless of the display it’s rendered on. The device just needs to be calibrated properly.
– The RGB model is additive. Combining more light creates lighter and brighter colors. This aligns with the physical properties of colored light.
Some disadvantages of RGB:
– It cannot represent all human-visible colors within the RGB gamut. Some shades, like dark purples, cannot be reproduced well.
– The relationship between RGB values and the perceptual experience of color is non-linear. Equal steps in RGB values are not perceived as equal steps in color.
– On its own, RGB does not specify other aspects of color appearance like brightness, saturation, etc. Extra information like color profiles is required for accuracy.
– The additive mixing of light in RGB does not correlate well with the subtractive mixing of paints and inks. So RGB struggles to represent the gamut of colors possible with physical pigments.
What is the RYB color model?
The RYB color model is based on the three primary colors used in painting and traditional arts: red, yellow, and blue. This is a subtractive color model, the opposite of RGB’s additive model. Paints and inks work by absorbing certain wavelengths of light and reflecting the rest back to our eyes. The more colors that get absorbed, the darker a color becomes.
The primary RYB colors absorb two wavelengths each:
– Red absorbs cyan and blue light and reflects back red.
– Yellow absorbs blue and violet light and reflects back yellow.
– Blue absorbs yellow and orange light and reflects back blue.
When all three primary colors are combined, almost all visible wavelengths get absorbed and the result is near black. As fewer colors are mixed together, more white light can reflect off the surface, creating lighter tints.
Some key advantages of the RYB model:
– It replicates the subtractive mixing of pigments and dyes. This makes it popular for painting as fewer color mixes are needed to produce a wide gamut.
– The primaries align with how human vision perceives color based on wavelengths absorbed by the eye’s cones.
– Many dark and muddy colors can be represented well in RYB. These are harder to create with the RGB model.
Some disadvantages of RYB:
– The exact primaries can vary based on the pigments used. There are no fixed RYB values like in RGB.
– The gamut of achievable colors is smaller compared to RGB. Many light tints and neon-like colors cannot be produced by mixing paints.
– RYB perception can change based on lighting conditions. A RYB mix under sunlight may look different in indoor light. RGB colors are more consistent.
– Digital devices cannot rely on RYB for color reproduction. Computing requires defined units like RGB values to store and display colors.
Key differences between RGB and RYB
While both RGB and RYB provide a means to quantify color numerically, there are some important distinctions between the two color models:
| RGB | RYB |
| Additive color model (adding light) | Subtractive color model (absorbing light) |
| Emission of light from screens | Reflection of light off physical surfaces |
| Compatible with digital systems | Compatible with paint mixing |
| Pure, saturated primaries | Primaries dependent on pigments |
| Fixed color values | Variable color values |
| Three primary colors | Three primary colors |
| White from combining colors | Black from combining colors |
| Limited dark color reproduction | Broad dark color reproduction |
| Consistent color across light conditions | Color changes based on lighting |
The choice between RGB and RYB depends mainly on the target medium. Digital formats like JPG or PNG images rely exclusively on RGB. Meanwhile, RYB is designed for paint mixing to achieve desired real-world colors. Converting between the two models is possible using color management software, but this can result in loss of color accuracy.
When is each color model used?
Here are some examples of when the RGB and RYB color models are typically used:
RGB model uses:
– Computer displays – Screens produce colors by emitting RGB light.
– Digital images and graphics – RGB allows consistent color representation across devices.
– Video and television – RGB signals encode color data for display screens.
– Smartphone apps and websites – On-screen content uses RGB color codes.
– LED lighting – Combining red, green, and blue LEDs can produce a range of colored light.
RYB model uses:
– Painting – RYB provides a wide gamut using few primary paints.
– Traditional printing – Cyan, magenta, and yellow inks approximate RYB for color reproduction.
– Textile dyeing – RYB dyes are combined to create different fabric colors.
– Color theory – The RYB model helps visualize color relationships.
– Art education – RYB provides a basic color mixing framework for teaching.
– Children’s paints and crafts – RYB allows recognizable primary colors.
Converting between RGB and RYB
While RGB and RYB differ in their primaries, it is possible to convert colors between the two models numerically. However, the translation is often imperfect since the two gamuts do not fully overlap.
To convert RGB to RYB:
1. Convert the RGB values to CMY (cyan, magenta, yellow) which is another subtractive model similar to RYB.
2. Determine equivalent RYB percentages based on the CMY values.
3. Optionally transform RYB back to RGB to visualize on a digital display.
Converting in the other direction, from RYB to RGB:
1. Convert the RYB percentages to approximate CMY values.
2. Convert the CMY values to corresponding RGB color codes.
3. Optionally convert the resulting RGB to RYB again to check color accuracy.
Due to the fundamentally different color spaces, multiple translations may be required to find a close RGB-RYB match. Even then, an exact conversion is often impossible for some hues. Color management systems utilize complex algorithms and lookup tables to achieve workable RGB-RYB conversions for different applications.
How human vision perceives color
The biological mechanisms of human color vision play an important role in how both RGB and RYB color models were developed. Here is a quick overview:
– Light enters the eye through the pupil and is focused onto the retina.
– Photoreceptor cells called rods and cones detect light levels and wavelengths.
– Cones contain photopigments that are sensitive to short (blue), middle (green), and long (red) wavelengths of visible light.
– Signals from photoreceptors are sent via the optic nerve to the visual cortex of the brain.
– The brain interprets ratios of activation of the different cones as different hues and colors.
– Rod cells also detect brightness and help distinguish fine details, gradients, and textures.
RYB aligns closely with the absorption peaks of the three types of cones. RGB matches the types of cones while also covering the visible color spectrum evenly and efficiently using primary colors.
Both models leverage the cone cells of human vision to reproduce colors effectively. This forms the basis for all color perception and helps explain common visual phenomena like color blindness. An understanding of physiology provides context for how these color systems were developed.
Practical applications and uses
Both RGB and RYB color models have practical real-world applications across many domains:
Art and Design:
– Digital artists use RGB to define colors for web and app content. Painters mix RYB pigments for canvases and prints.
– Graphic design relies extensively on choosing and specifying colors. RGB is used for on-screen design, RYB for printed materials.
– RGB lighting rigs are used in concerts, events, and smart homes. RYB continues to have traditional stage lighting uses as well.
Science and Research:
– Microscope and telescope images use RGB colors to map wavelengths like x-rays or infrared to visible colors.
– Satellite imagery and geology maps apply false RYB colors to convey vegetative health, mineral deposits, and terrain.
– Medical imaging modalities like MRI convert tissue data to RGB colors to visualize anatomy and pathology.
Photography and Cinematography:
– RGB sensors in digital cameras capture images. RYB filters can adjust color balance and styling.
– Photo editing software uses RGB color channels to adjust hues, saturation and brightness.
– Movie production uses RYB gels on lights to produce atmospheric effects and colors on camera.
Manufacturing and Textiles:
– RGB LEDs light up electronics like TVs and smartphones. RYB dyes color fabrics from clothing to furniture upholstery.
– Product prototypes are 3D printed in RYB plastics before mass production in final colors.
– Car paint mixing uses RYB bases to achieve custom vehicle colors.
In summary, both color models continue to serve important yet distinct purposes across disciplines like science, art, commerce, and entertainment. While RGB dominates the digital world, RYB remains vital for tactile color applications.
Conclusion
RGB and RYB provide two fundamental ways to represent color numerically. RGB defines colors using primary hues of light. RYB is based on primary pigments. RGB fuels the digital world of screens and images. RYB enables physical color reproduction with paints and inks.
While the two models have key differences, both deliver colors that align with human visual perception. Converting between RGB and RYB is possible but can result in loss of accuracy. Each system has advantages and disadvantages based on the target use case. RGB serves computed graphics, while RYB provides the foundation for color mixing by artists.
Understanding these color models helps create, interpret, and transform color across fields like photography, design, and publishing. Whether colors are emitted as pixels or reflected off inks, the foundations of RGB and RYB enrich our visual experiences.
