I based it on this https://gameaccessibilityguidelines.com/ensure-no-essential-information-is-conve...
Namely "there are several other less common conditions that affect other colours ... - ... even achromatopsia, a very rare condition where you have no colour vision at al, and colourblindness acquired through brain/nerve damage, which can alter colours in very unpredictable ways, even swapping them around."