you need to contact your Toyota dealership or another paint shop for the exact color of paint that you need. I believe that Toyota sells the tins of thier paint for about $44 each.
7th Gen Celica color codes can be found at..https://www.celicahobby.com/tech/colorcodes.html
If your kit is Polyurethane, the paint needs to be mixed with a catalyst so it will bond to the polyurethane... When using a polyurethane paint, strain the paint prior to mixing the catalyst. (your painter should already know this part though
but even before your aftermarket body kit parts are painted (no matter what they are made of), you'll need to primer them.