I was thinking about this recently and figured that the main reason all craftable items didn't get a color palette, was memory issues. Given the age of the game, this in all likelihood is no longer a problem. So is there any other reason this shouldn't be allowed, aside from the work involved? I'd personally be willing to work on making new textures for the items so they can accept two colors, if it's something anyone feels like it's worth pursuing. IMO, why not maximize the potential of decorating, and let folks paint their weapons too while we're at it?
I've also thought about expanded palettes to add some vibrant colors. The palettes for clothing in the game in particular always seemed too subdued, feeling more like a middle-ages game rather than a futuristic sci-fi one.