I would wear a tie with both pink and black in it, or with combinations of pink and grey and black. One classic purpose of a tie, at least in modern times, is to "tie" your clothing colors together. But think of it this way. If you choose a tie of one color, a pink tie will probably just blend into your pink shirt. A black tie will sort of disappear into your black vest. If you can find an all-pink tie that is considerably darker or lighter than your shirt, that might work. But a black tie with a black vest, in my opinion, is a bad combination. When I wore vests, I never wore a one-color tie that matched the vest. In fact, I had such a combination once and never wore it because it looked odd. ETA: In classic movies, Cary Grant can pull off a grey tie and a grey suit because he goes for different shades of grey. But black doesn't really have shades, does it?
The best way to be sure is to try it out. If you need to buy a tie, wear your stuff when you go out shopping. If you like the way something looks, go for it.
You said that people from other schools go to your dances. Is there any chance of asking a girl from another school, or a girl that you know socially who doesn't go to your school?
