Personally, I find rock to be my mortal enemy. That whole thing where it forms in clusters and veins in the 'parent' rock without fail ruins any sort of delightful symmetry I had going on, at least color-wise. Microline, gypsum, even magnetite ruin my day. Not to hate on magnetite, as my dearest dream is to have a fort where I can make a magnetite mine separate from the rest and later use it as a tomb - or, better yet, a fort where I could incorporate a mined-out deposit as the dining room or barracks or something without it looking too hideous. I also have a mild distaste for copper in general as it seems to rear its ugly, low-value head more often than not in my forts.
In a perfect world, I'd probably go for having the great majority of the fort (ie, sans farms) hewn from something gray (granite, while a fairly pedestrian stone, would probably be my choice). I've also found myself intentionally doing things with red stone - most often kaolinite. I believe I used it as grates in a fort that had magma channels under all the floors once upon a time. I'd also like some stuff made of olivine just because that's totally awesome, not to mention green being my favorite color. I've also been known to plan 'realistically' with my shops (using the most easily recognizable realistic rock) and with making nifty things out of marble, but I don't bust my ass over it.
Largely, though, I've made my peace with the rock and just use whatever's handy for a strange mish-mash of random colors everywhere. I've become increasingly irritated at bright white flux stones (most recent fort is apparently a mix of marble and dolomite everywhere), but I'll just have to live with that and the increased value that'll no doubt bring an immigrant flood.