Is it normal for fish to change color overtime? I’ve had my…

Is it normal for fish to change color overtime? I’ve had my betta fish, Kai, for a few months now. When I first got him, he was a deep blue, almost like ink. But lately, I’ve noticed his fins are turning reddish, and a lighter patch has appeared on his side. He seems healthy and active, but the color shift has me curious (and a little worried). Is it normal for fish to change colors over time?