It has been known for some time that Boa constrictors are able to change phases of colors during certain periods of the day. We looked into this in cases of some specimens in our collection.
What factors have effects on color changing? As etology of reptiles, especially snakes is not totally understood yet, we have no definite answer to that.
What certain is that most Boa constrictors have a tendency to wear dark uniform after being fed. We noticed this on almost every specimen, independently from subspecies or localities. We have an unproved theory what could be the cause of that. According to our view, snakes prefer dark colors during digestation to absorb more heat due to their darker-than-usual tone. Temperature, humidity, stress may also play role in that in our opinion.
It is important to notice that some localities have more tendency to change phases, while other have less or don't have at all.
Our Nicaraguan boas (Boa c. imperator) are showing darker phase from the morning till the afternoon in contrast with nightime and dawn. Peruvian redtail boas (Boa c. constrictor) do the same. However, Ecuadorian boas and Honduran boas (Boa c. imperator), furthermore Tumbes boas (Boa c. longicauda) are barely showing this phenomenon.
Hopefully, the actual reason behind this phenomenon will be revealed by time.
1.1 CB 2009 Pearl Island boas
(Boa c. sabogae)details..