Admittedly I am far more fastidious about these things than most people but I have found the genitive colours (noun + noun) less flexible to write with when integrating a %color substitution in clothing prose.
I would personally find them much more adaptable if they just kept their descriptive noun, so:
jet
licorice
ebony
raven
midnight
onyx
sapphire
azure
periwinkle
charcoal
heather
burgundy
ruby
cherry
olive
emerald
jade
pear
lime
