@DBActiveChicago Manual of Style doesn't address blonde vs blond but refers to the AP Style Guide and the Merriam-Webster dictionary:
First, note that the AP Stylebook updated its advice in 2020, when its entry for "blond, blonde" was replaced with an entry for "blond" under "gender-neutral language." (Subscribers to the AP Stylebook online can discover this by searching for "blond.") The new entry continues to advise using blond for the adjective regardless of gender (the feminine e ending is from the French). But it advises against using either blond or blonde as a noun except in a direct quotation, advice that applies equally to brunette (which, however, is rarely spelled brunet).
Though CMOS doesn't cover this topic, we like AP's new guidance, which discourages writing that would reduce people to physical characteristics or gender stereotypes (as in a phrase like "the blonde in the front row").
As for Merriam-Webster, Chicago usually prefers first-listed spellings over any variants; blond is the first-listed spelling for both the adjective and noun forms, so that's what we'd prefer. The entry for "blond" in Merriam-Webster doesn't currently (as of June 1, 2021) include a usage warning (cf. "broad," which Merriam-Webster labels "slang, often offensive" as a synonym for "woman"). But AP's advice suggests that it is best to be cautious when using either spelling as a noun.
Who knew that using it as a noun was sexist. I actually follow Grammar Girl's:
Most of the time, inanimate objects are treated as male. For example, if you have a blond wooden dresser, "blond" is spelled without the E. A recent exception though is that Starbucks uses the feminine form for its opens in a new windowblonde roast coffee. Maybe the marketing people believe we'll love it more if we think of it opens in a new windowas a woman or as female.
1. Avoid using "blond" as a stand-alone noun for men or women if you can easily rewrite your sentence or you think it may offend your readers.
2. If you do use the words as nouns, maintain the gender difference and use "blonde" for a woman and "blond" for a man.
3. Inanimate objects usually get the masculine form of the word.
4. When you're using "blond" as an adjective, use the masculine spelling, without the E, especially if you're in the United States.
Grammar Girl also addresses fiancé and fiancee:
Two that you may have seen before also come from French: "confidant" (and "confidante") and "fiance" (and "fiancee"), The AP Stylebook says to uphold the gender difference for both words, unless you need a gender-neutral option for "fiancee," and in that case, it recommends describing couples as engaged or planning to marry. The Chicago Manual of Style doesn't address "fiancee" and notes the feminine form of "confidante" but says it's fading from the English language.
