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    <p>Paint works by absorption. You start with white light (255,255,255) and multiply it by the absorption factors.</p> <p>Blue paint absorbs all red and green light that hits it.</p> <p>Yellow paint absorbs all blue light that hits it.</p> <p>In a perfect world, that means that combining yellow and blue paint would result in black paint, or at best a muddy gray. In practice the "blue" paint has a bias towards green, so you get a muddy green. I've never seen an example of mixing yellow and blue that produces a satisfactory green. Wikipedia goes into some of the complexities of this process: <a href="http://en.wikipedia.org/wiki/Primary_color#Subtractive_primaries" rel="nofollow noreferrer">http://en.wikipedia.org/wiki/Primary_color#Subtractive_primaries</a></p> <p>I think what you are really asking is how to interpolate colors along a color wheel. This should be independent of whether the colors are absorptive as in paint, or emissive as in RGB displays.</p> <p><strong>Edit:</strong> By working in the HSL color space you can get the kind of results you're looking for. Here's some code in Python that implements the algorithm; averaging hues is tricky, and is based on a previous answer of mine <a href="https://stackoverflow.com/questions/5343629/averaging-angles">for averaging angles</a>.</p> <pre><code>from colorsys import rgb_to_hls,hls_to_rgb from math import sin,cos,atan2,pi def average_colors(rgb1, rgb2): h1, l1, s1 = rgb_to_hls(rgb1[0]/255., rgb1[1]/255., rgb1[2]/255.) h2, l2, s2 = rgb_to_hls(rgb2[0]/255., rgb2[1]/255., rgb2[2]/255.) s = 0.5 * (s1 + s2) l = 0.5 * (l1 + l2) x = cos(2*pi*h1) + cos(2*pi*h2) y = sin(2*pi*h1) + sin(2*pi*h2) if x != 0.0 or y != 0.0: h = atan2(y, x) / (2*pi) else: h = 0.0 s = 0.0 r, g, b = hls_to_rgb(h, l, s) return (int(r*255.), int(g*255.), int(b*255.)) &gt;&gt;&gt; average_colors((255,255,0),(0,0,255)) (0, 255, 111) &gt;&gt;&gt; average_colors((255,255,0),(0,255,255)) (0, 255, 0) </code></pre> <p>Note that this answer does <strong>not</strong> emulate paint mixing, for the reasons stated above. Rather it gives an intuitive mixing of colors that is not grounded in any physical world reality.</p>
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    1. POAlgorithm for finding the color between two others - in the colorspace of painted colors
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    1. USCommunity
    1. USMark Ransom
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    1. POAlgorithm for finding the color between two others - in the colorspace of painted colors
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    1. COUsing HSL seems to me the good answer. I use HSL for a few problems (like producing random sets of constrasted colors) and it gives results that are very coherent with the human eye experience.
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      1. USDenys Séguret
    2. CO@Mark How would you adjust this if you had uneven amounts of colour - say 30% red + 70% blue?
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      1. USglenstorey
    3. COI try to emulate real world color in my UIColor+Mixing category. It mixes in RGB (computer style), RYB (real world, additive), and CMYK (real world, subtractive). The algorithms are pretty simple and you can adjust the divisor (based on the number of colors) to get more of what you like. No limitations - have fun with it - https://github.com/ddelruss/UIColor-Mixing Enjoy.
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      1. USDamien Del Russo
 

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