It’s tempting to say, we should use the original English, which is British English.
Some suggest the original English remained in Britain when the North American colonies were founded; others claim it was brought to the Americas by the British settlers, leaving a pale imitation back in Britain. The truth is much stranger: the original English was actually smuggled out of Britain to the West Indies in a wardrobe belonging to General Sir Ralph Abercromby, where it ended up on the island of Trinidad after Sir Ralph took possession of that territory in the name of the British Crown. It came to be used and modified freely by the various immigrants to Trinidad (and later Tobago) and their descendants (largely African, Indian, British, Portuguese, German, Spanish, and Chinese). Many of these peoples then emigrated, bringing the original English to North America and back to Britain. A copy of it has fallen into my hands, and so I can, without bias, make the following call: both color and colour shall be acceptable in Haskell programming. 'Kerb' and 'gaol' are right out, however. Cheers, Robert (who's grandfather is from London and grandmother from Trinidad; but is nevertheless American)