Most of the paint on vehicles is not a simple open the can, pour into a gun and paint. There are more steps to it then that. They will need to have a specific primer color and type. Some of the paint is 2-3 steps as far as what and how you lay it down. Then there is the clear-coat that needs to be applied. There are some paints that are only one-step but color selection is limited. Look in the yellow pages for an auto paint store in your area and go talk to them.
Have you tried rubbing the paint out to get rid of the oxidation ?
The paint is sort of receding away down to the primer, in areas exposed to lot of sun. Fortunately, the primer is silver-grey and my paint is (was) silver-blue, so it's not as noticiable as it would be if my truck was black or some other dark color.
I guess it's a little more involved than I thought. Though another option might be to just paint the whole truck, rather than trying to match the bed and the cab. I heard of some guy that did a killer paint job on his car using a countless layers with brush and then sanding it smooth after each coat. But I'm sure it was not his first paint job, and it probably took weeks of work.
I wonder what Maaco would charge just to paint a bed?