NES could visualize only four colors for each sprite

[Hypercat-Z]

...trasparent included.
If it wasn't for that his graphic would have been improved a lot:


http://www.duelinganalogs.com/article/th...never-was/

[DidYouKnowGaming]

This is a well known technical limitation of the console. Also, it's not per sprite, it's per sprite tile. That's why Mega Man has 5 colours + transparency. He has multiple sprite tiles.