Without pictures, I'm only going off the description (can I be any more obvious?) but it sounds to me that the yellow may be a female. The biggest question I got when inquiring about the sex of my geyri, was the belly coloration. Light in color and pretty solid was going to be a female, while the colored with prominent black stripes would prove to be a male. Turns out, they were all correct. Hope that helps. The picture is of Runako's belly. He was supposed to be a "she" but isn't. Oh well.