Turns out that, while an interesting effect, the ‘coloured-in map’ look is a bit tricky to do, at least if you’re me & you’re using raster data.

Probably easier if I was using some sort of vector layer approach, so maybe that’s a thing to look at? ( I’m supposed to be doing some species of online mapping thing for work purposes next year anyway, … )

Also, both the Northern line & Jubilee line look pretty much the same in Colour & B/W. Should have seen that one coming.