I have excellent colour vision but I still struggle with this because it's hard to remember which shade of green is which when flipping between the map and the legend

I'm not even color blind and I hate it.

That said, in my color green they won't need a visa, but they will get a 30-day visa exemption. If they want to stay longer they'll need to apply for a visa.

There's a blue in the middle.

They all means the same - free to travel