I have pants color teal blue and shirt light green. I want to color the pants and shirt black? What?

It depends on what you are using to color them. If it isn't very good, the colors you will end up with could be darker versions of those colors, some variations of grays, or it could even turn out to be some of the colors used to make up that black (black dyes are made using multiple colors such as blues, purples, reds, and others). The black colors could turn out just fine, but they may eventually wash out. :)