It wasn't red; it would have been a streaky cream/pink. The dope was applied to the
outside, with the first two, usually, a 50/50 mix with thinners, which soaked in (and through.) Large a/c were covered in Irish linen, which is a creamy colour, while light a/c used Egyptian cotton, which tends to a whiter colour.
Edgar
Like this:-

or, maybe, even slightly less:-