The Little-Known Reason Pencils Are Yellow
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Gabrielle Hick, for Artsy:

“Competing pencil makers colored their pencils yellow and gave them Oriental names to suggest that the graphite they contained was equally good,” Petroski said.

And it worked. An oft-repeated bit of pencil lore tells of an experiment conducted by Faber in the middle of the 20th century. The company distributed 1,000 pencils—half yellow, half green—to a test group. While both sets of pencils were identical apart from their color, the green pencils were returned en masse with complaints about their shoddy quality.