have you tried taking the glass top off to see if that is magnifying it?
when trying a light with exact layout i did notice the effect you speak of a bit but did not see the color separation at all (i did have it raised up about 7-8" off tank so that might be the difference).
Just to be safe i would see how it looks with no glass top to make sure that is not what is making the problem for you.
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Nick
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