I've read that if two colors hyphenated for singular type that means it is combination colors. If not, then it has part colors like:
A1. A blue-green shirt is turquoise.
A2. A blue and green shirt is one which has parts that are blue and parts green.
but if we are talking about plural, then that doesn't mean combination, like:
B1. She has only blue and green shoes. Means: that all of the person’s shoes are either blue or green
B2. She has only blue-and-green shoes Means: that the person’s shoe collection consists only of shoes in which each pair is blue
and green.
Same here:
C1. Yellow, pink, and red flowers refers to flowers colored yellow, pink, or red.
C2. Whereas yellow-pink-and-red flowers denotes tricolored flowers.
Which you prefer A1-2 or B1-2 OR C1-2
Best Answer
These rules seem overly prescriptive.
We do sometimes use the two colour names to indicate an intermediate colour. So "A blue-green shirt" is a turquoise.
The expression "She has only blue and green shoes" in ambiguous. It could mean that she has some blue and some green shoes, or it could mean all her shoes are patterned blue and green. Using hyphens can reduce that ambiguity in written English. But if a completely unambiguous sentence is required, then you would have to rephrase.
The example with flowers is similarly ambiguous. If it matters, then the expression could be rephrased. The hyphenated form is ugly and difficult to say, so wouldn't be used in practice. Normally it doesn't matter much if the flowers are individually red, yellow and pink, or pattern with red, yellow and pink, so the ambiguity can be allowed to remain.