This is the best answer I've seen. Basically the color tells you where the bleed is occurring. On/near the surface will be bright red and indicate likely fissures or hemorrhoids, while dark red to black color indicates a bleed further up the digestive tract which can be something much more serious.

Apparently doctors get asked this A LOT and a little red blood when you wipe is very normal. However, best thing to do is talk to your doctor to be on the safe side