Then I can't help much. I've seen Cumberlands that look like that, but I've also seen aberrant redears that look like that. The few yellowbelly X redears I've seen had more elaborate postorbital marks, but hybrids are usually variable, so who knows.
I am thinking it is a hybrid. maybe 2/3's yellowbelly 1/3 RES? or vice versa. Most of the 50/50 hybrids have distinct marks behind the ears that are unique to them but if it is a diluted hybrid it would be difficult to distinguish from either ssp.