Leaving "correct" anatomy on the side , i still think you should fix some minor details regarding proportion and position.
The outline itself isn't bad (except some parts that look unnatural, like the top of the head that is too squarish), and adding colours isnt the problem either; The thing is that you are not doing much with what you have.
You should increase the contrast between the shades, so they "pop" out more; also, the inner lines that are supossed to be muscles, are very weird in structure, and in my opinion don't really mix with the current anatomy style you have going on.
Also there are a couple of stray pixels (white) on the hands, and another couple on the knee area (skin tone).
Kee it up tho, with a bit of work, this could really be improved.