do bettas lose their colour?

Question
Hi,
I have just bought two male bettas last week (I sent you a different question a day or so ago, so thankyou for your response, it was great!).  Just the other morning, I noticed that my red one had lost a lot of his vibrant colour over night (he was very bright when I bought him from the pet shop).  He seemed lighter and duller in colour but he was no less active, he still swam around quite fast.  The colour of my blue one had not changed at all, he was still really bright. I thought my red one might have got the chills so I put a light over the tank to heat it up a bit, and he seemed to get better by the afternoon.  Then i removed the light because it got a bit too hot and i haven't put it back since (the water is usually fine at room temperature).  He was fine the next morning aswell but then became slightly lighter again by the afternoon.  I did nothing to change the water temperature this time.  Now he is back to his old colour, all vibrant again, all by himself with no water temp change.  Have you ever had fish that went through periods where they lost their colour?
Thankyou for your help :)  

Answer
Hey again, Jessica-

Some fish, like bettas and gouramis, change their color according to their mood. Dark, vibrant colors are displayed when the fish is feeling dominant, especially excited, or in the mood to breed, whereas pale colors indicate boredom, fear, or as you said, cold. Color changes can also indicate changes in the weather or barometric pressure. Amazing little guys, aren't they? Also, genetics can play a part, as red is a fragile color in bettas and most will fade over time.

Hope this is helpful, and as long as your little guy is acting fine, you've got nothing to worry about.
-Amber Worman