Tons of things to consider here not even related to being a boat. Just basic paint questions need to be answered first.
Type of original paint and compatibility with the patching paint?
Dealing with a clear coat?
Is the original faded?
Are you looking for custom mix that's perfect or shelf color that's close enough?
Are you looking to roll and tip, rattle can, or compressor?
Are you talking about scratches or panels?
You may find the dealer brand offers a touch-up, you may find a topside quart that's close, you may need a scan from an automotive paint store, you may even find a Rustoleum rattle can that works.
Needs more info.