My snake has red ink on its belly!!!!!

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Hello everyone! I'm new to the forum. My name is Fletcher, I have a 4-5 year old, 4' California King Snake named Zombie. Well I made the mistake of putting paper towels, with red colored designs on them, as a substrate and now Zombies belly is bright red from the ink.

A- is this harmful to the him, should I take him to the vet?

B- Is there any way I can help to clean it off?

I bathed him in warm water yesterday while I cleaned his tank out, but he still has the red ink all on the underside of his body. Zombie doesn't seem aggravated or sick but I'd still like to see what I can do for him. any advice will be much appreciated.