Hmm, so interesting.
I like it. 
But the 1 colour pictures doesn't exists xD, if you have only one colour in a picture just this is a BK with this colour.
this is a 2 colour pixel art, and if it have a transparent pixels with 0 opacity, now you have a pixel art with 3 colours.
It is. I was on holydays and i had some free time, so I desided to make some 1-colour picture with oldschoot thematics.
It's quite an inspiring piece and I like the style you have here. It looks as though it could be one long level in the popular mobile game Snake.
This is 2 colours.
1 - black.
2 - transparent.