Marker
Although it hinges on “in a way that the artist may not appreciate”, so I guess if you have their permission beforehand it’s ok?
Misanthrope
I believe it’s technically disallowed under Rule 1:
Do not upload images that have been altered in a way that the artist may not appreciate. This may include (but is not limited to) removing an artist’s signature and/or watermark, recoloring an image to insert or remove an OC, upscaling artwork, and fetish edits.
Although it hinges on “in a way that the artist may not appreciate”, so I guess if you have their permission beforehand it’s ok?