If you're in a marine tidepool alongside an octopus, and you accidentally startle it and cause it to ink, would the ink leave a stain on your skin or clothes? (The clothes in question are a pair of swim trunks, if that makes a difference.)
(If it helps, ink from the cuttlefish (a close relative of the octopus) is the source of sepia ink. Anyone have experience with that?)
From Google, I looked up "Does octopus ink stain?" and just "octopus ink," and at Wikipedia, I looked up "octopus" and "octopus ink". I didn't get any definitive answers, but I learned that octopus ink is composed largely of melanin, so I Googled "Does melanin stain?" At first, I thought I had answers, but then realized that most everything was referring to culture stains.