The new edition of The Chicago Manual of Style has a nicely laid-out hyphenation guide (in chart format) for compound modifiers (7.85). Most of the rules are the same as before, with one notable exception: colors.

In the 15th edition (7.90), compound modifiers for colors (e.g., emerald green, bluish green, coal black, a green and red dress) were not hyphenated, whether they came before or after a noun, with the exception of “established expressions” like black-and-white, which were hyphenated when they came before a noun.

The 16th edition now suggests hyphenating when the phrase comes before a noun, not hyphenating if it comes after the noun, which is the rule for most compound modifiers. Their examples:

     emerald-green tie
     reddish-brown flagstone
     blue-green algae
     snow-white dress
     black-and-white print


     His tie is emerald green.
     The stone is reddish brown.
     The water is blue green.
     The clouds are snow white.
     The truth isn’t black and white.

CMOS-16 says, “This departure from Chicago’s former usage serves both simplicity and logic.” I agree!