when I was a kid I had watched a lot of british programming when we lived on military bases in germany and italy because it was the main way to watch things in english, and then later I gravitated (unintentionally) towards books by british authors (or authors hailing from places otherwise previously colonized by the UK)
so as a kid I spelled things: grey, colour, analogue, cheque, mould, tyre, etc in part because I kept seeing them spelled that way, and in part because of feeling like "grey" felt more like "grey" than "gray" to me.
But I kept getting teachers who would be like "stop! using british spelling!" so I had to always remind myself about words like colour and mould and such.
but now I live in a country where they lean more towards british spellings, so I've come full circle. (if only i'd had an intense desire to learn french as a kid instead of spanish and german.)