Yes, your Colorado is from 1988. I have a twin to your bike - in the same teal color. I have two 1988 Colorados - One bought new, and the second off of CL a couple of months ago. From the photos, everything on your bike looks original except for the tires. That is amazing. I have no idea of the value, but I don't imagine much. Maybe another member has insight on the value. Good find!