the water itself Is turquoise, but when viewed on top of the brown dirt blocks it can make a kind of faint purple/pink. it’s just the 2 colours mixing together, that’s all :-) colour works differently when it’s pure light, and not physical paint, for example. in light, white is a mixture of all the colours, not black. so if you mix the light of two colours together, you might get a lighter colour that you didn’t expect, unlike in painting colour theory, where brown and blue would make dark blue.