I wear jean everyday. I do mean everyday, since I don't wear any other type of pants or any shorts at all.
Never have any jean blue stain on my Titanium interior for 1+ year & 20k miles with my E.
Even you have a darker color interior, your jean will still stain, & if you look carefully, it still will show. It may not as visible as lighter color interior, but it still is there.
Personally, I always wash any dark cotton cloth with warm water at least once before wearing it, specially jean, just to ensure it does not stain.
I also try to vacuum it 1st if I have any stain on the seat, before I try to use any water for any stain. I was amazed how much simple vacuum clean up some stain w/o any water on our FXC fabric seats.