Hi Abby,
This is going to be a tough one! Resin does not like to stay on a curved surface, so know this is going to be anywhere from a challenging to frustrating project.
First, you will want to start with a doming resin. These mix thick enough that they want to stay on a flat surface and not run over the side. We have several in our store: https://shop.resinobsession.com/collections/resin/doming
Next, I would suggest mixing the resin, then letting it sit for longer than you ordinarily would before applying. The thicker it gets before application, the more likely it is to stay on the surface. The problem with this is that if you introduce air bubbles at this point, you are less likely to get them out.
Please know too that the resin will blend at the edges. i.e. You are not going to have clearly defined lines between the colors.
Good luck and let us know how it goes!