Betta changing colour in seconds

So I recency got a crown tail betta. My sister actually bought him for me. I was told he was black with blue on his lower half and an orange tail. When I got him he was not really black, rather more of a Grey and we chalked it up to the lighting. But he continued to get more and more pale. I only noticed within the past 3 days.
Today I thought we would do the fin excersizes using a mirror next to the tank and a minute later I looked over and he was picth black with royal blue scales and a bright orange tail. It only happens when he sees another betta or his reflection. I've read about marble bettas but he changes and changes back in seconds. His name is Merlin and I think tht with all of this in mind he may just be magical! Has anyone seen this before?
Pictures and videos below:
Before


10 seconds later




I have video of it happening in 5 seconds but can't seem to upload it. If anyone wants it I can post on YouTube and link it. The video is much more clear on the change.

 

Wow! You indeed have a special betta. I've never seen it myself before, but I saw this on an article mentioning why bettas might change color quickly:
"Marble coloration in bettas is a result of a mutation known as a 'jumping gene' This gene is able to move between the fish's chromosomes, resulting in an ever changing color pattern. Marble bettas are just as healthy as fish without the jumping gene but may experience a variety of color changes throughout their lives. Some marble fish start out solid turquoise only to end up a few weeks later with a red-and-white butterfly pattern."
Hope this helps!

 

No clue what’s going on but that is so cool! Is his tank big enough/does he otherwise have enough stimulation? Sometimes they go pale when they’re unhappy, but who knows he looks pretty healthy.

 

Wow! You indeed have a special betta. I've never seen it myself before, but I saw this on an article mentioning why bettas might change color quickly:
"Marble coloration in bettas is a result of a mutation known as a 'jumping gene' This gene is able to move between the fish's chromosomes, resulting in an ever changing color pattern. Marble bettas are just as healthy as fish without the jumping gene but may experience a variety of color changes throughout their lives. Some marble fish start out solid turquoise only to end up a few weeks later with a red-and-white butterfly pattern."
Hope this helps!

I saw this article too, but whenever they talk about the colour change, they say over a week or so. I can't find anything otherwise! Very strange!

 

No clue what’s going on but that is so cool! Is his tank big enough/does he otherwise have enough stimulation? Sometimes they go pale when they’re unhappy, but who knows he looks pretty healthy.

He has a 20 litre tank and 3 tank mates who he really likes. They keep him busy, and I've tried to make it full of plants and hide holes for him. He is very active. I also thought he may be sick until today. But as soon as I take the mirror away, he goes pale again! He flares his fins while playing and when there is food, and turns slightly darker at the same time, so I think the fun flaring and colour change may be an adrenaline reaction, or maybe excitement? I don't know. But he has a huge personality

 

That's so very cool! You most certainly have a very unique betta fish. Hope the best!