Bruce, Johanna, et al.:
There are some (possible) additional
example sentences which might serve to add more information (I can’t
really say “clarify matters,” since they don’t, and I’m
not sure if I can get away with a neologism like “murken”):
(1) ….the bright reddish star above center is Betelgeuse
(example from http://www.cosmographica.com/gallery/portfolio/portfolio301/pages/342-GalaxySouth.htm)
(2) The blood also looks bright red because oxygen isn't being used by
the peripheral tissues.
(example from http://www.bio.miami.edu/tom/bil265/bil265goods/20_lung2.html)
While there are exceptions, being able to
put –ish on something tends to position it as
an adjective, and people apparently do use ‘bright
red’ as an adjectival subject complement. While it would be possible to
argue that (1) is to be read as “the bright and reddish star,” there’s
nothing to force that reading (no comma, etc.).
Bill Spruiell