Butterfly

Aah, now I see it. Thanks for the info Horo.

Banding Depending on the monitor you use, you might not notice it. Look towards the corners. We can see steps between the blue, it's not a smooth fading. It is not very pronounced but clearly visible. It might be the jpg compression, too.

Banding? I give, what is banding?

Very good. perfect, every choice seems to be the right one. The issue is the banding, which should not be there. Make sure you use 48bit dithering, it's purpose is to smooth out gradients. Sometimes even 48 bit dithering cannot fix all banding, but most of it can be dithered out.

I'm not sure why, but I really like this.

that deep blue disturbes me a bit, p-p-perhaps a white background? :)

Looks nice (not boo).