This may seem like a trivial thing, but item coloration actually matters a lot to me.
In particular, hot green, purple and yellow look extremely cheap to me. It always bothered me a little to use set items in D2 just because they looked cheap.
I really hope they use the D2 shade of Gold (this isn't exactly it) for uniques, and don't choose a coloring scheme similar to WoW or HG:L. The blue that was used for magic items does not bother me because it's a muted magical looking color, not a "hot" shade.
Actually, I'd love it if they could have colors be like gold, silver, bronze and glowing and have all these colors be slightly animated..ie, you see the metallic font colors faintly shimmering, and the magic ones faintly glowing/pulsating.