Would it be a good idea to spray paint my yoyo even if its only a little bit? Like just spray once and then let the paint fall on the yoyo on its own. Not directly sprayed. Thanks 
In my experience, not the best idea. Sweat from the hands can dissolve this kind of paint and it will end up on your fingers.
If you must, do it on a surface that is not touched much, like the cup of the yoyo (if you don’t plan on fingerspining) or under the clear caps for example. Medical fuel or zippo fuel are great for removing it and making a pattern on it, not sure if they would cause some sort of reaction with certain types of plastic tho …
Spray paint probably won’t be your best bet. If you’d like to paint a yoyo, I’d recommend using an airbrush. It would help for the yoyo to be raw. You have to prime then apply multiple even coats, but none too thick. In the past, a clear coat has always finished it off.