This is really good.
I like how vibrant all the colours are, and I'm glad that they have a scheme, his (I assume it's a male) shoes, headphones, liquid inside him, etc. they all compliment each other perfectly. And that you gave him a personality making him, not just a drawing but a character.
As good as I think it is too have coloured lines, I don't think they should be brighter than the background. It's not as pleasant to look at large if it's done with pixels, what I'm saying is this drawing is like pixel art, that doesn't want to be pixel art, so don't think I'm against pixel art when I say that.
Well done, I hope this feedback was constructive.