Casting into a spherical mold

So I’ve been having some issues casting into a silicon spherical mold with a diameter of 4 inch. I now know That I should’ve used casting resin but i still have the issue of the max casting limit. The casting epoxy I bought has a limit of 6 ounces which is not enough for the sphere. Because of that I know I have to pour layers but the thing is I have no clue how to keep the same color if I’m using layers. I’m new to dealing with epoxy resin but putting more color pigment or less will change how the resin looks I’m assuming so how do I deal with that?