8 bit means 8^2 colours, no matter if its in a sprite or a background

these are 3 bit (max 8 colours) and 2 bit (max 4 colours)

actually monkey. the 256 colors is the limit for the backgrounds and tiles in 8bit. sprites are limited to 4 colors

Ingore the left one,jesus.

And i can't shade the right one more,it won't be 8bit anymore

This could use a bit more shading. Also, you don't need to call it 8bit unless you restricted yourself to 256 colors. I'm hoping 3bit (8 colors) is closer to the mark.