Also not sure what you are asking...
You can stain the epoxy/ resin using pigments That you paint over the fiberglass. You can stain the fiberglass itself with dye prior to resin/ epoxy. You can even paint over top of resin with all sorts of paints. Or you can leave resin/ epoxy “clear” to let the fiber product show (see carbon fiber). But that requires specific resins/epoxies.
If you are looking for a clear resin, West Systems 105 & 207 are my go-to product for clear resining.
If you are going to paint it... Bondo car body stuff does the trick and is readily available at most hardware/ automotive shops.
Resgardless of what you use, safety first, the fumes from this will mess up your lungs. Only operate in a well ventilated space with an appropriate respirator. Also use gloves and be careful not to get it on yourself... it can be a skin irritant too!