A pretty trivial matter but helpful for accurate portrayals of people like Dante Alighieri and Francesco Petrarca as they’re often seen wearing hats. The Portrait of Dante absolves the issue over whether if Dante had blond or dark hair suggesting that his hair darkened with age. (I remember reading another source with Dante implying that his eyes were green.) Logically, Petrarca’s red-haired but it’s likely his hair colour would’ve decomposed after his death.
Parsimoniously, the same book suggested that Petrarch lied about his hair. When they dug up his grave, people discovered his real hair colour. There are no known pictures of them without their hats in their lifetimes. If it does show up for either one of them, it could confirm my suspicion that their actual hair colour would’ve been mis-remembered over time.