Hi,
Looked at the pics and to me the colour looks like bog standard red primer, would darken down a little once coated with a acrylic varnish top coat. The anti fouling red is a slightly different shade and doubtless not red primer. Would suggest getting a can and giving it a go on some scrap plasticard and then see if youre satisfied with the colour match.
Matching colours is not necessarily an exact science as two people looking at a red double decker bus for example will see two different shades of red, even as an individual you can verify this but looking at a colour picture with alternate eyes covered up, you will notice colour variance between your left and right eye and vice versa. Even looking at colour photos of boats and more so older ones will show variances in colour, depending on the film used, the light conditions, the age of the photo and even when a photo has been digitally reproduced can have an affect on the colour representation. At the end of the day it is what pleases your eye and what you are satisfied with. You will always get the one person that says such and such colour isn't right and there is one too many rivets in such and such plating etc. If youre happy then that is all that matters!
Hope this helps
Dave