Wow, how strange! My car has 2-tone leather seats (dark & light grey) and I wear jeans all the time - never had a problem. My car is about 1-1/2 years old now. I tend to wear lighter colored jeans though, not the really dark indigo. Interesting!!
You're never too old to wear jeans in public, though, is my opinion! Of course, I'm 40 and dye my hair black and bright purple and wear Chuck Taylor sneakers, so maybe I shouldn't be listened to for fashion advice. ;-)