Betta Fish: Will his body turn full blue

I’ve had him for a few weeks now since he was given to me for free by a guy who bought aquatic plants from me. I really liked his color from the start,he was a lowkey pink with a red spot on his head. I’ve noticed his color slowly changing, and I’m excited to see what he’ll look like as he grows.

Some parts of his tail are transparent; at first I thought it was a tear, but after looking closely, it wasn’t. I wasn’t expecting him to grow this fast since I’m only feeding him live ostracods and whatever other live food I can find in my tanks. He’s actually quite chunky right now because I once released him into a tank filled with live food. Luckily, I noticed how big his tummy was getting and moved him into a small tank temporarily.

He doesn’t have a name yet since I’m planning to rehome him with a 5g tank and plants included.