This one is older and a manga (so not colored), but it deals with cutting.
https://www.mangago.me/read-manga/cut/
https://www.mangago.me/read-manga/fragmented/ but the full story can only be read in the app because they stopped uploading it here :/
https://www.mangago.me/read-manga/yagiza_no_yuujin/ (HIGHLY RECOMMEND)
https://www.mangago.me/read-manga/annarasumanara/ (author/illustrator went WILD with this artstyle)
https://www.mangago.me/read-manga/look_alike_daughter/ (MC has a legit and diagnosed behavioral disorder)
https://www.mangago.me/read-manga/the_djinn/
https://www.mangago.me/read-manga/i_love_amy/ (i would say that amy is arguably mentally ill, though that may come from her circumstances as well)
https://www.mangago.me/read-manga/gachiakuta/ one of the characters suffer from CPTSD for sure, and while you don't get to it until much later (and this whole plot doesn't rlly revolve around suicide/mental illness other than that), it's a very strong point of their character.
https://www.mangago.me/read-manga/dead_mount_death_play/ (kinda. the main female character)
this manga has depictions of mental illness/social stigma throughout (and in a pretty realistic format), but it's pretty episodic (so it's a reoccuring theme but not the main theme of all arcs) https://www.mangago.me/read-manga/kurosagi_shitai_takuhaibin/
Thank you, everyone!
Any recs with suicide attempt/thoughts or self harm? Or other mental illness stuff you can think of. Pref colored :)