There is no way to recolor Mia currently. I've seen videos uploaded online with recolors - as far as I can tell, those are done entirely with video editing, and are not like that in game.
There will be controller compatibility as soon as I'm able. I don't know about a sprite editor, but adding some alternate coloration to Mia would be doable - but something I'll still have to save for later due to the extra work involved and how Mia's sprites are still being updated/changed during development.