Wow that's great. Only suggestions would be to add a little bit of white on the stomach and the left (Magmortar's right) arm cannon, and perhaps change the orange to a brighter, more yellow colour. Remember, you can pick colours outside of Magby and Magmar.
And now that I look at it, the right leg (Magmortar's left) would probably look better if it was one pixel lower / longer.
And now that I look at it, the right leg (Magmortar's left) would probably look better if it was one pixel lower / longer.