Even though I'm new too,
I've done some reading
(sorry no links handy) and
to be as non-specific and general as possible,
I think it does vary from species to species.
Like, (and noone flame me, I'm just thinking off the top of my head)
Phrag Besseae imparts a red small shape,
and so does Sophrinitis (I think that's the right name,
the small red South American member of the cat. alliance)
so these cases red is dominant,
but in phals i seem to remember that it's hard to get a red
that's not purple or pink.
but anyway, from one newbie to another, I think of it like
a ladder, not a binary system,
where one trait could constantly get "one -upped" by another.
For some really good reading,
here's a thread you might have already seen on ploidy,
but when I re-read it paying attention
to the heterozygous and homozygous parts,
in the context of inheritable traits,
it really added a new dimension: