User blog comment:Lord Loss/Monster Hunter Theory... Blog/@comment-4212769-20120331162339/@comment-4212769-20120501122624

I want to make it a bit clearer:

The young and adolescent are Green/Red due to the small amount of sexual hormones. When they get fertile they search for a mate with changing colors (like many birds). Through the higher amount of hormones they get Pink/Azure (adolescence is over). When they found each other they mate and reproduce. While these process the amount of hormones declines and they get back to Green/Red. That's why the Rathian in the ecology cinematic in MHFU is Green while she feeds them. When the offspring grows old enough to care for themselves they could mate another time and change the color again. What means older Rathians/Rathalos can still change colors to Pink/Azure. And after they made babies again they lose the color again. This explains that Pink/Azure and Green/Red can be the same size.

Another theory that they have the same size is they just have a genetical size (like human) that differs of every Rath. And when they get the ultimate size they get (about that time) fertility.

When they lose fertility they get Gold/Silver because of the lack of sexual hormones. But like the anon said they mate for life so they stay together even when they're old.

If they only mate once in life they change only one time in Pink/Azure. But this can change if...

... the babies die and the parents are still fertile. So they would get again to Pink/Azure to reproduce again.

... the mate dies. That would mean the remaining Rath needs to find a new mate to reproduce (or when the Rathalos dies and the Rathian is already pregnant then a new father for the offsprings (but when the eggs are laid already).) and turn again to they're Pink/Azure appearance.

For this wall o' text I want some responses :P