I just picked up a cute little boy betta yesterday from a pet store.
He's normally sort of a blue-black, but I noticed something interesting when I picked him out. He gets red spots along the base of his anal fin when flaring or agitated. I know it wasn't light or water conditions because I was observing it a bit in the pet store: he was in the same water and just blue/black, but put next to another betta he would flare and gain these red spots. Otherwise he seems to be a healthy and very active fish (I found some bubbles he blew this morning when I woke up).
I could add photos if you like because I think the flash also bothered him enough that he showed his spots.
When my delta tail male betta flares, his colors get brighter, so i think that what your betta does is him trying to improve his color to impress the male and look like the prettier one. That is completely normal
One of the many fascinating things about bettas is their ability to change colour based on mood, stress level etc.
For example, when you change your betta's water his colour will fade, and he may even develop "stress lines", dark lines which run from his nose to his tail. This colour change is normal, just a response to having his home disturbed. Once the stress of the water change is over, his colour will return to normal.
Feel free to post pics of your betta anyway - I'll bet he is gorgeous with his red spots! :)
Yeah, I had read that many get brighter/paler based on their mood, I just had never heard of one that gained a color! I suppose he may just be very, very dark red that only reads as red when he's agitated.
It is part of the genetics, that eventually for whatever reason some or a lot of the fishy's end up having, I have also seen this on some fishy's when they are in a new enviornment, and start to flare, their colors that are meant to come out, start to show..even in a few weeks to a month when you first get a betta, they are about 3-6 months, about an adult, but then thier fins get longer, and their colors really peak, and some literally change, most will be bursting with those bright reds, and blues.
My rescue right now is starting to show more red, when I first got him, he was sick so he looked a dull gray..then he went to a brighter blue, which he still is, but now I am seeing red mixing in with the blue..it's quite awsumm how they do this..")
This pic is my rescue now in a 3 gal after treatment, I will upload the other one in a bit..it's on my phone, when I first got him..it's an amazing difference.. If you look in his Ventrals, and anal fins, you can see some red peaking