I am not sure the part of blushing (maybe he was just happy?) its giving me hisoka blush malicious vibe . In Kiss me of you Dare, Grayson was described as psychopath too so he copies emotion of the other even if not feeling it and there is a possibility he is delighted being challenged regardless who is the challenger. And that part also he is very conscious and calmer to meet Dane for the Third time since he doesn't of there first and second meeting. But as for release of pheromone I think its Grayson subconscious Habits, cause he is a dominant Alpha. (Maybe i am wrong?)

Guys I have some questions,
In chapter 8, why was Grayson blushing and looked overly happy when he was told he would be taking the test with Dane?
In chapter 9th why Grayson looked at Dane like that? Then suddenly releases pheromones?
What happened during those hours they disappeared during the test?