Betta Fish: Samurai Betta with Red Stripe in Tail?

Excuse the dirty looking tank – I took this photo right after a water change so a bunch of dirt got kicked up.

Meet Tiger, the samurai Betta we've had for about 7 months. Over time, he's developed a red stripe at the base of his tail. Is this anything to be concerned about, or just a normal bit of color popping through? I don't care about the strict samurai coloring, I just want to make sure this little dude is healthy.

Also, we didn't know about all the issues with samurai coloring until after we brought him home (I'd never even heard of this variant until my daughter picked him out). But he's ours now, and I'm giving his little genetic mutant self a bougie betta palace as long as he can enjoy it.