My female just did this for the first time ever today. I've been slowly introducing her to a prospective male since the summer. The first intro was a DISASTER. She HATED him. Turned black, gaped, tried to bite him, just not having his crap at ALL. Then he doubled his weight and the next intro, she sat still, didn't gape, but didn't seem all that into it either. Today, she turned bright green and head bobbed at him, and he turned purple and turquoise about the head, his horns got red, his body got this gorgeous electric lime stripe and he started bobbing too. I'm starting to think they might have some chemistry!