Tobiano - Color generally remains on face (a true Tobiano will have an unmarked face), chest, and flank. The legs are usually white below the knee and white usually crosses the back between the withers and tail. A two-toned tail is common.
Frame - Color "frames" the horse's body, so white does not cross the back. Frame does not put white on legs, but likes to put a lot of white on the face.
Splash - The horse quite literally looks like it was picked up and dipped in a large bucket of white paint. White patches start at legs and work their way up to the body. Face usually has bottom-heavy white markings.
Sabino - Causes roaning (not to be confused with the roan gene itself) and jagged edges on white patches.
That's a pretty basic description of each, but you'll learn the differences in each from looking at pictures and seeing them yourself.
OMG THANK YOU FOR POSTING THIS! I have been trying to figure out the difference in the "paint" colors for like 3 weeks and never was really sure if I was looking at the right pictures etc. FINALLY I think I get it! The pictures are a great help, im a visual person and I kept saying to myself these last few weeks that I just need all the patterns standing next to each other!