Here's a low-res image of the '88 sales brochure specs page:
But here's the deal. The sales brochure does not list what color combinations could be available or ordered. I think that the "1988 Source Book" that the dealership used would list the 2-tone combinations that could be ordered, but I don't have a copy of that. I can't imagine that certain 2-tone combinations, such as Regatta Blue and Scarlet Red, were ever made.
From looking at the sales brochure, it looks like there two different 2-tone styles in 1988. There was the standard 2-tone ("Deluxe") in which the second color in the middle of the sides, and the Eddie Bauer style ("Unique") in which the contrast color was on the lower sides only.
As you may know, the door sticker, the "compliance" label, will show the truck's original paint codes.