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The following image has three circles of RGB Red, Blue and Green on a White Background. Each one has 50% opacity. The stacking order is green, blue and red.

The overlapping areas have tints of dark green, purple and brown.

How can one predict these overlapping tints? Is there a theory to predict this?

Essentially, I would like to know how to produce region of a third color using two existing overlapping colors in Illustrator.

enter image description here

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  • what do you mean: which color is going to be produced if you mix 3 colors? or How to know which 3 colors to mix to obtain a known color?
    – Luciano
    Jul 21 '16 at 15:05
  • Are you asking in a math perspective of adding different opacities of colors and what the combined color will be or just generally asking when colors are mixed what will the color be (Ex: Mixing red + blue = purple)?
    – AndrewH
    Jul 21 '16 at 15:05
  • @AndrewH well, to start with a general idea of what might be produced on mixing two colors would be good
    – Amit Saxena
    Jul 21 '16 at 16:43
  • @AmitSaxena In simple terms, RGB is an additive color model, so when you add a certain percentage of 2 or 3 colors (Red, Green & Blue), you will end up creating a new color. There is a pretty good write up about this on stackoverflow - Calculation of a mixed color in RGB
    – AndrewH
    Jul 21 '16 at 16:53
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If you are wanting to generate a second or third color by overlapping shapes as in your example, and want to do so accurately as it would happen in an RGB color system. You can use the transparency modes in illustrator. 'Overlay' and 'screen' will be your best options for replicating light-based color behavior.

see image below. (tip: you might need to use a black background for the shapes in "screen" transparency mode)

enter image description here

If you want a mixture as far as paint would behave (not light-based colors.) then you can use 'multiply' transparency mode. If you want to use the primary colors you should probably adjust them to cyan blue, magenta and yellow. But I kept your colors anyway.

enter image description here

Finally, if you wish to color pick the overlapping areas you probably will be disappointed when you realize the color picker will just copy the properties of one of the shapes (whichever is over the other). So my advice is to rasterize the image and then color pick the overlapping areas.

To rasterize the image: - select all three circles with the transparency mode applied - Go the menu 'Object' and choose 'Rasterize'

( make sure you duplicate your circles before you do this if you want to keep the original vector)

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