We have sold lots of garages and many, many hangars in white. It's mandatory to use a white pigmented non yellowing urethane topcoat as if you use a clear over white epoxy alone it will turn gray and yellow over time, especially if any sun hits it in ares as true epoxies are not uv stable and without a white protective topcoat you will most likely not be pleased in a year or so.
We had had a number off calls from people over the years that purchase white floors from other suppliers who were not aware of this issue, or failed to advise about it, and we had to come up with systems to repair and recoat these floors.
If you plan on using flecks, apply the white urethane onto the white epoxy and fleck into that, and then apply a clear topcoat. We carry all of these products and can assist with setting up his system for you.