If it's anything like my Angel, it has to be completely normal. Mine does that as well. Based on where he is in the tank, lighting conditions, or if he is stressed for some reason (usually because I'm using the magnet to clean the glass!).
Thats a relief. I never owned an angel before and wasn't sure about this. He is brave tho, swims up to my hand in the tank, and is the only fish that doesn't freak out when I clean the outside of the glass on the tank.
Yes they are cute creatures. My angels are very friendly. Sometimes too friendly, when I vaccuum the gravel they think my arm hair are worms and pick at them!
And it's not cute then - it feels like a tweezer picking at me!
pretty normal for angels to have disappearing stripes.
much less pronounced in other color morphs..ie marble etc..the kois may get lighter on their gold crest.
I have wild angles that change striping and 'mood' spots..when they are really comfortable..their markings are very pronounced..stressed..the stripes are gone.