Like the word 'said', writers are constantly looking for ways to describe their characters aside from the usual fallback of pronouns and the characters' name. Occupations, hair coloring and relationships are the usual culprits. For instance: "The blond ran down the hall" or "The plumber pulled up his pants" and "His girlfriend pouted." All of these are fine, like everything else, in moderation, and it goes without saying using these kinds of descriptors is the anvil equivalent of 'telling, not showing'.
Descriptions of 'the red head' or the 'blond' are, mho, the worst of the three types of descriptors. Hair color is very rarely an element of plot or character development and is one of the easiest ways to describe a character's appearance; hence, constant mentioning gets annoying because it adds little, if anything, to the actual story.
Repeated use of the descriptors also runs the risk of reducing a character to that one phrase: The blond, the girlfriend, the plumber. These are all characteristics of the characters -- they are not *the* characters -- and indeed, these should not be the only elements of the characters we're told about (or rather, shown).