Presumably this refers to an increase in net heat absorption compared to not having paint
. This makes sense to me only if the paint
properties (including colour and surface finish) causes more energy from the sun to be absorbed - and/or less to be radiated away - than the alternative, which would more likely be gelcoat than raw uncoloured glass-reinforced resin.
For anyone wanting to wrap their minds around this, I suggest some research into emissivity
Older eggs (such as my 1979 Boler) were generally beige, while new ones are generally white, both in gelcoat. I don't see how painting
one of those old shells yellow or bright blue or whatever other light
colour (even the original beige) would make the heat absorption situation worse. Common sense would would seem to suggest that black might be unwise for most applications, such as mine which sits outside in summer sun, but I don't have any solid evidence for that.
I think the original quote is based on the incorrect assumption that any paint colour will be darker than the original fiberglass colour.
The hints in the link from Chester make really good sense to me - thanks, Ches.