Here's a great tip to help painting crisp taped edges where you are using two colors of paint and the taped edge is the border of the two colors. The problem most people have when they try to paint two colors like this is paint seeping under the tape due to the texture of the wall and making the edge look ragged.

To keep this from happening, paint with your base color first and let it dry completely. Then tape the edge. Now normally people would start painting with the second color. Don't. Use the base color *again* and paint the edge as if you were painting the second color on. When you do this, the base color will fill in any small crevices under the tape. But since it's the same color, it'll look fine. You can then paint the second color on top and it won't seep under the tape since those nooks and crannies will already be filled with the base color. This leads to really crisp and clean edges between the two colors of paint.