Well, I'd want to be sanitizing those sheets which would fade black sheets in no time. I'd probably get gray sheets:

I hope you have a moisture-proof mattress cover, as you'll likely have to replace the mattress if not.

https://www.sheex.com/products/original-performance-sheet-set?variant=18028646498375

Just returned from #2DD's place. She has black sheets--paired with lavender bedspread. Dk Navy Blue could work for sheets also....

IMO black sheets are not going to solve anything and use some oxyclean when you do laundry . How will black sheets keep you from washing them. Maybe get blue or some other color but honestly the color of the sheets is not the issue .An airbnb is not supposed to be a permanent rental unit so not sure what you are doing . If this is arental then he can wash his own sheets .

IMO white sheets show sweat but have the ability to be bleached, black sheets show other bodily fluids and can’t be bleached… I think you need to pick your poison here

@Patricia Colwell Consulting I had been using bleach and oxyclean on white sheets but it was only removing the sweat/yellow staining not the gray/black dye transfer; when I make the bed the sheets look so gross because of this. I figured the black sheets would help with masking the gray he is getting on the sheets. He stays for weeks at a time and has been a fairly good customer in all other aspects, we’ve just worked something out for a weekly rate since he stays so often. In between his long visits others will stay and I use a different white sheet set. I do like to keep his room clean and made while he is here so I thought the black sheets would work best but the houses theme is airy and light sorta a studio McGee style and black sheets seem pretty dark and not a very organic vibe.

I'd go with gray. Just wash them once a week - I assume on days the don't get washed he makes his own bed?