First guess would be somehow your seats were blue to start, but that is highly doubtful. Have you looked at your seat belt to see if it is showing blue in the same basic area of contact? If you find it on the seat belt, it is more probably a transfer from something you are wearing that is blue.
Do you wear blue jeans? If so it might be blue jean dye transfer--a common issue with light interior colors. It should clean up with some good cleaners. I have had this problem with my Kalahari interior. My first solution was to simply get an inexpensive ($25) auto parts store seat cover in tan that I used all the time except for shows.That worked fine. Lately I have not been using it but I am very careful to place my left hand on the bolster and back into the car, rubbing my pants on my hand rather than the bolster or just keeping my jeans off the bolster. I have not had a big problem but it is now showing some darkening so I probably should give it a cleaning before I put it up for the winter anyway. --Bob
The area shown in your pics gets a lot of contact getting in and out of your car. I'm guessing it's from your clothes. I've noticed that on my blk interior so I take extra care to avoid dragging my body against the side bolsters or use a terry cloth seat cover and make sure it covers that area when I enter the car as much as possible.