According to the actual definition no it does not

It is with several colors. And it is ok. So why do you need a monochorme? You start idea as monochrome, and now you have a few colors theme!!!

you could say it's a 4 bit color (it can fit up to 16 different colors) I counted at least 8 in your sprite.

I reduced it to 6 tones. It looks good.

Yes it is! I suppose you will use it in a game? Looking good!