Spread doesn’t hide color the way it does pattern (see above), but it does influence the expression of the color alleles. So a spread bird isn’t simply spread, it’s spread plus a color: spread blue, spread brown, or spread ash-red.
You can think of the 'spread' allele as taking the color of the tail bar and spreading it across the entire bird. So while spread ash-red may seem like an unexpectedly light shade, the phenotype makes sense when you realize that ash-red birds have a light-colored tail bar.
Breeders are often inconsistent in how they name different colors of pigeons. For instance, spread ash-red is sometimes called "solid mealy," and spread blue is often called "black." The color-naming inconsistencies probably date back to a time when we didn't understand the genetics of color and pattern as well as we do today. To add to the confusion, some colors are difficult to tell apart, and colors that are the same geneticically can look different phenotypically in different breeds.