Quote from Roger Sweet's book Mastering the Universe:
Another misfit from Big Jim was the Big Jim gorilla. I suggested redoing the creature for Masters and mocked up a prototype. I changed the ape's body color from black to bright yellow and gave him a dark olive-green face and chest. His face was contorted, with white teeth snarling in an open mouth of blood red. I gave him a black body harness. From his shoulders, I hung a dark maroon cape.