I wonder if this may interest you?
There was a pink sky in the original impression of Hokusai's woodblock print "Great wave off Kanagawa." It’s just faded in so many copies that we don’t think of The Great Wave as having a pink sky. -- see Art Institute of Chicago, "Seeing Triple: The Great Wave by Hokusai," April 3, 2019. https://www.artic.edu/articles/743/seeing-triple-the-great-wave-by-hokusai
Before now, frankly, I didn't give any thought to "the atmospheric pink and grey in the sky" -- see "Hokusai: the Great Wave that swept the world" (John-Paul Stonard). The Guardian. 19 May 2017. https://www.theguardian.com/artanddesign/2017/may/19/hokusai-japanese-artist-late-blossoming-great-wave-mount-fuji
According to Tim Clark of the British Museum, "the pink in the sky was from a vegetable dye." -- see "This Might Be Your Last Chance to See 'The Great Wave' in Person" (Nathaniel Ainley). Vice. May 9, 2017. https://www.vice.com/en_us/article/8qwqe3/last-chance-to-see-hokusai-great-wave-in-person
Maybe Hokusai's fugitive pink sky comes from a pigment made from safflowers? -- see see JAANUS (Japanese Architecture and Art Net Users System), "beni"紅http://www.aisf.or.jp/~jaanus/deta/b/beni.htm
@chikara
Cool! Thanks! 🌊