I'd shoot a full bait using one of the color you want for the belly, un-mold it and slice it in half right thru the middle making sure that the portion at the gate is trimmed back so it won't impede plastic flow and then stick the bottom half back in the mold. Close, clamp, and re-shoot using the second color and injecting super slow. I'd use plastic heated to about 355-360 for the second color. Instant two color ddgill.