Fading away....Brazilian rainbow boa

I took my rainbow boa with me to get some mice and I noticed that I dont see its irridesence (sp) colors any more as much on its body not even in the sun. I only see it on the head is this a sign of an u p and coming shedding? or is there something else that i am missing?

I have been feeding him every 5 days two mice a week. He's growing faster than I thought he/she would..

If your feeding an appropriate sized meal (big around as their widest part), then I suspect there is a shed coming up. Check the belly, if it's pink you know it's coming. Bump up that humidity higher than the usual 70% for when he goes blue.