Most experienced painters will tell you your chances of successfully painting silicone caulk are not good, even if you use spray paint. You'll be trying to make your spray paint stick to a surface that is designed to resist any kind of moisture. But if you insist on painting silicone caulk, good preparation and the proper type of paint will give you the best chance of success.
Best Silicone Caulk Paint and Preparation
If you can find oil-based spray paint to use, first prepare your caulk surfaces by removing some of the non-stick surfaces by rubbing it with denatured alcohol. Then apply primer and your spray paint.