Personally, I think the consistent colors suck. Too boring for me. More color the better. But to answer your question, a color change for a tile has to be pushed from a server. So a dev can not offer color options from within their app, unless thy already have a push server setup, as with live tile apps, to push the change. Smart Tile is one of very few apps (possibly the only) that offers about a dozen color options for their tile which they push from their server. I wish more developers (I have contacted all the transparent guys) would offer color options, or at least offer transparent or their default tile. With the ability in Mango to update apps without the need for a server hopefully there will be more options.
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