Microcline is the same color as a swordmaster.
Cobaltite is the same color as a craftsdwarf or axe lord.
Kimberlite is the same color as a fisherdwarf or guard.
Garnierite is the same color as a jeweler or elite marksdwarf.
AFAIK, those four stones are the only ones of their respective colors.
Edit: forgot to reply to what I was originally going to
Ah, that's right: ash > (lye) > potash > pearlash?
I think microcline is the same colour; I'm not sure since I've switched to the modified, "natural" colour scheme. Cobaltite is a nice light blue, though (it's just a bother that a tiny seam of it happened to run straight through my dining room; now it looks like we've had trolls for dinner).
Yup, that's the production chain for pearlash. I find it's a lot easier to use the job manager for that sort of thing. If you queue up a sequence of:
Make ash (30) -> Make potash from ash (30) -> Make pearlash (30)
You'll wind up with 30 pearlash without having to micromanage the workshops. You can do a similar sequence if you want to use the lye step.
As for colors, you can put a construction (typically a floor) down, and when you remove it, it'll be the same type as the base layer. That is, if you find a cobaltite vein in a quartzite layer, putting down some floor constructions on it and then removing them will leave you with quartzite cavern floors.
Incidentally, this makes a handy way to "upgrade" floor engravings.