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I think in 7.5 e-on did in fact change how diffuse light color works for all indirect lighting models.  It now relies exclusively on what you set the "overall skylight color" to.  This makes more sense to me as the additional "Light Color" box is redundant.  To change the color to your original blue, set the Overall Skylight Color."

Here's the answer to your light color issue (solution is from Dave Burdick). I have display issues as well, luckily they're more irritating than show stoppers