Ok, this is vague yet vivid for me. An 80s or 90s film with people that either have a colored crystal (blue, yellow, and maybe red or purple,) that I believe determines what "class" they are. I think they are engineered. I remember one scene they are going through a desert in a sand storm, riding in military transport style vehicles with 6-8 wheels. The crystals I think are on the back of their hands or on their foreheads, and may affect their eye color. This is NOT DUNE. I believe someone that may look like Patrick Swayze was in it. The plot isn't clear to me. Not much to go by, but thanks...
In the 1994 film Island City,
Citizens of the city wore a colored crystal on their sternum and could only mate with other citizens of the same color, which was based on the individual's genetic makeup.
The city is surrounded by a desert-like wasteland, and the opening credits include an eight-wheeled armored vehicle.
Could be a bit of a long shot, but this sounds like it might be Logan's Run. Released in 1976, although perhaps you saw it on TV or home video in the 80s/90s.
After surviving a global conflict, the survivors of humanity live in a controlled environment, and are not allowed to live beyond 30 years. At age 30 they are taken to be "reincarnated" (spoiler alert: they're just killed.)
Each person has a crystal implanted in their hand at birth, which starts off white and changes colours as they grow older. IIRC, it turns red when it's time to go get "reincarnated."
Here's a picture of Logan (Michael York.) I dunno how much he looks like Patrick Swayze, but maybe the mists of time took their toll? (Note: I tried to upload the image directly, but SE said it was too big.)
I don't recall any deserts or military vehicles myself, although it has been a long time since I watched the movie. There was, however, also a TV show that featured some scrubby terrain and these things. (Again, can't upload the image... I'm wondering if there's a plugin in my browser that's messing with my ability to use the site...)