English words like "brunette", "blonde", and "redhead" refer to people of a particular hair color. Are there similar words in Latin? It is easy to express hair color in English or Latin with several words: "a girl with red hair", virgo crinibus rubris. I am looking for adjectives or nouns like my three English examples. I doubt that phrases like virgo rubra would be as easy to understand as "redhead", but I will be gladly proven wrong if color words can be used this way.
Color words are used in the manner you describe, and virgo rufa indeed means a redhead. For example, the L&S dictionary gives references to nuntia fulva Jovis "golden[-haired] messenger", and exactly vigro rufa in (Ter. Heaut., v., 5), where Clitipho refuses to marry rufamne illam virginem, / caesiam, sparso ore, adunco naso.
Also, there is a reason why Rufus was a common Roman surname!
I doubt ruber could be used as a hair color description, though, except maybe for special effect. The adjective refers to the color of blood, setting sun and red paint, and may be understood in many contexts as scarlet, crimson or ruby red. You would rather describe in such a way someone who dyed their hair (bold) red, as opposed to the naturally occurring red hair.
ADDEDNUM: I found a reference to ruber signifying a hair color in (Mart. XII., 54):
crine ruber, niger ore, brevis pede, lumine laesus,
rem magnam praestas, Zoile, si bonus es.
Arguably, crinis ruber is as hyperbolic here as calling Zoile's os niger is. In my thinking, this is rather an example of the "special effect" usage that I mentioned above.
Certainly "flavus" in the sense "fair-haired", as in Horace 4,4:
Qualem ministrum fulminis alitem,
cui rex deorum regnum in avis vagas
permisit expertus fidelem
Iuppiter in Ganymede flavo,
Likewise "rufus", and, I should think, others.