Why do Cresties "Fire Up"?

[Pareeeee]

My young cousin posed this question to me today and I wasn't really sure how to answer. It's an interesting question, and actually something I've always wondered but not really researched.
We all know that Cresties "fire up" but why?

These were my theories:
My crestie, Rodney, tends to fire up depending on the lighting. Not whether or not he's awake or asleep. When he's sleeping, whichever side is facing the light is fired up, and the other side in the 'shade' is pale. (I have a cool UV light on his tank for plant growth)

I think they do fire up more when they are active, but it really seems to have something to do with lighting.

I just took these quick photos now.

This side was facing the light, and you can see where the light hit him between the leaves of the plant he was hiding in.
http://i.imgur.com/WyGz95b.jpg

This side was almost completely in the shade.
http://i.imgur.com/kWucHT7.jpg

Shot from above.
http://i.imgur.com/tockQkl.jpg


Anyway, I thought it was cool.
What do you guys think?

[Charis]

I'm not sure all the reasons they fire up but they do it with changes in humidity, when they are hunting, mating and a number of other reasons. I've even seen some of my baby geckos fire up or down to better blend in to their surroundings.

[Hurrok]

That is a very interesting question, never really thought of why. Seems like a pretty good defense to blend in to their surroundings among other things.

Nice example here though! It's cool to see the difference :)