The colour that was really just marketing
I'd always assumed London buses were red for some deep, historic reason, tied to royalty or tradition or something equally grand. It's really just a very good bit of 1907 branding.
Back then, dozens of rival companies ran omnibuses through London in every colour you could think of, a total muddle in the smoggy streets. In 1907, the London General Omnibus Company painted its fleet bright red simply to stand out from that crowd. It worked so well that when London Transport formed in 1933 and absorbed the competition, it kept the red and rolled it out across the network, although for years afterwards, buses running out on the fringes of the capital were actually painted Lincoln Green instead. The red that feels so essentially, permanently London was really just one company's attempt to beat its rivals, and it simply outlived every single one of them.
I painted one in watercolour and ink, that unmistakable red against grey London streets. There's a poster with a letter home and a postcard if you'd like one.
Shop the poster here: Red Double Decker Bus, London · Travel Poster