I'm pretty sure you can get paint for tiles. Depending on where they are, it is possible to tile over existing tiles too - I've heard it can be a pain in the whatsit though!

Astrid's right about uncovering scary stuff. We've found that nothing in our house is square, so we have an extra half a tile's width in one part of our kitchen/dining room! DH fitted fly screens to the windows and doors and we have a huge gap at one end of each of the sliding doors cos they're not square either.
When we moved in, we thought our kitchen was just ugly and old fashioned, but we soon found out that hardly anything in it worked (dishwasher, 3 out of 4 stove elements and the oven had exposed wiring in it!) so that became priority no 1 instead of the bathrooms. And we found some pretty shoddy workmanship too e.g. the stuff surrounding the shower wasn't waterproof - fortunately no damage to the structural timbers!