we hired a non-pro to paint our homes interior with quite bold colors...at the corners where the different colors came together he used caulk...is this normal?...what is a good way?

Caulk is quite handy to use in corners. The reason for it is that most walls have some kind of texture on them. Taping off the corner will result in bleeding and a jagged line. When you are using different colors on adjoining walls, it it hard to get a clean line in the corner because of the texture on the walls. Running a bead of caulk down the corner and smoothing it with a finger will level out the texture in the corner so a clean straight line can be achieved freehand.