Ok, I'm not sure who posted the video of doing a poured and then injected core shot, but it inspired me to waste some plastic and see how it worked on a multi cavity mold. I suspect it will depend on the mold, but the effect was pretty interesting.
On the right is watermelon shot through white pearl, and on the left is white pearl shot through watermelon. Both were done in a 4 cavity mold. I like them both.