DDA banding

You can't miss these pink stripes on the pillars at Denmark Hill station. But why are they here? Some sort of heritage leftover? Some kind of coloured identifier? Something to help train divers brake accurately? And once you start seeing them, you see them everywhere. They're also pink at Morden South, so maybe it's a Thameslink thing. But at Chislehurst they're blue. And at Tattenham Corner a sort of turquoise. Also why are there two painted bands? One at roughly head height and one at chest height. Is it a precision thing? Keep looking, and it seems a lot of them are dark blue. Blue again at Grove Park, which like Chislehurst is on Southeastern. But also blue at Hounslow and at Malden Manor, both of which were once Southwestern. And not just in London. Here are blue stripes on a white pillar at Christchurch and white stripes on a blue pillar at Stockport. White stripes again at Hartlepool... but now seemingly no consistency in height. You can also see them on the London Underground.…