You have this listed as having 3 colours, but it has four. Black, tan, and the two AA colours.
I think the AA is a but chunky in places, especially on the line down the character's shirt. Perhaps try using just one AA colour to start? Four colours seems unnecessary here, and because their values are so different, using them both seems to add noise instead of smoothing the image.
Some wonderful work! Should definitely keep it up with the AA practice, it's a good thing to try to master!
Thanks for the feedback, I'll give it a change when I get home today!