# Color Subtraction

1. Oct 6, 2011

### JSGandora

1. The problem statement, all variables and given/known data
What color results when yellow and blue pigment are combined?

2. Relevant equations
W=R+B+G

3. The attempt at a solution
Since yellow pigment absorbs all wavelengths except yellow, then adding another pigment will absorb all the blue pigments so shouldn't the resulting color be black?

Or if the pigments mean that it reflects yellow and blue, then I think the resulting color would be white.

However, the answer key says green. I don't understand why...there is no solution either.

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Last edited by a moderator: Apr 26, 2017
2. Oct 6, 2011

### I like Serena

Hi JSGandora!

You appear to have landed in the murky area what exactly is which color.

When you are talking about pigments, the primary colors are usually named "yellow", "red" and "blue", which is what we learned in primary school.
However, in the world of printing these colors are actually closer to "yellow", "magenta" and "cyan".

So I suspect that when you were asked to combine yellow and blue, you were really asked to combine yellow and cyan (which is sort of light blue).
In that case the resulting color would indeed be green.

3. Oct 6, 2011

### JSGandora

Hm, that's quite ambiguous, considering that on a Science Olympiad Optics test. Thanks for the help! :)

4. Oct 6, 2011

Agreed!

5. Oct 6, 2011

### phinds

Yep ... I've often been startled to find how frequent it is that folks do not realize how ambiguously defined such color issue sometimes are.