Ever notice that powered drink mixes like Kool-Aid or Gatorade are a white power but as soon as you get them wet they turn blue or purple or whatever color. How is this?
The powder is mostly sugar; the bits that add color to the water are colored, but are only a small percentage of the overall amount of powder, but that’s all it takes to change the water’s color. The whiteness of the sugar is dissolved completely in the water, and doesn’t affect the color one way or another.
I think that there’s a reversal there too… just as sugar is white when solid and colorless when in aqueous solution, I think that there are pigments or other compounds in the mix that reflect certain colors much more strongly while in solution than when they are in powder form.
Exactly what the scientific explanation of this phenomenon is I don’t know. 
Any really bright chemist dopers out there wanna give it a shot?