Poor choice of colours: distinguishing between the orange of 2025 and the red of 2040 is very hard, especially considering most people will read this on a small phone screen.
I don't want to talk down your issue, but on my 5" screen they're easily differentiable. Which colours would be better? Something like a colour gradient in say green with a different projection?
I guess depending on size and colour rendition of displays it can be easier / harder, but overall I'd still say it's a poor choice.
A choice of different colours is OK, but specifically those 2 are pretty hard to distinguish. Simply changing one of them to black, which looks like no other colour used in the map, would be much better.
I don't think a gradient works for colouring a map like this: we can distinguish gradient colours when they are next to each other, but if 2 countries far away have adjacent values the colours would probably be too similar to tell the difference.