There are CSS theme tweaks for markdown reader "White" theme. The reader is for Android, supports LaTeX formulas and at the moment it doesn't ask for suspicious permissions - Epsilon notes: Markdown editor by Eugene Kartoyev. It's a reader because right after opening the file it renders and shows HTML/JavaScript (so it's not advised for files that you do not trust). Editor options are available only after that. Tweaks change font, it's color and size as well as text align.
The viewer mentioned works great in combo with iA Writer: Note, write, edit. by Information Architects GbmH that is a great editor (it opens the file in editor mode first). It even has nice code highlights and also doesn't ask for suspicious permissions. But it's really bad at editing external files: in order to export the file back to where you opened it you should move it to public area inside the app. Then go to .../Documents/iA Writer via file commander, rename the file (yeah, the app copied and renamed the file you opened) and copy it to the original place. So now I'm not sure if it's a good idea to use the app after all...
Also worth mentioning MGit by Manichord Pty Ltd that is a git client for Android (GPL). It is useful for maintaining markdown files on GitHub or GitBook (the latter supports LaTeX formulas).