You can buy Lowe spray paint from any distributor.
I used to run a body shop and I've told more customers than I can remember that "you can't match faded."
If you touch it up, you're going to see it.
If you are looking for a really good paint job, scuff the entire boat, prime any bare aluminum with etching primer, sand everything one last time, wash with degreaser (Dawn dish detergent works well) wipe down with thinner to remove any contaminates (fingerprints) or dust from sanding, wipe with tac cloth and spray or roll and tip.
If you do not have a Lowe distributor in your area, check out Parkers Duck Boat paint. Their green is good and flat and dries out nice. It's also easy on the pocketbook at about $15 per quart which should be plenty to do 2 coats on the outside.