You are correct partly Carrie,
In Japan and Germany, as far as I know, many traffic lights had been changed to a new standard as RYB for red yellow and blue to avoid colour blindness issues but it may take so many years until the whole world realise the issue, so I am not talking about any specific country but a general case.
About the purple thing, that would be colour psychological interpretation and it is a very interesting issue.
You may imagine that each human being is in fact seeing different colours in an absolute sense but each of us have seen a colour sample with green written under it so every time we see “that” colour (whatever it really looks like) it is green, even if we were perceiving cyan or pistachio. Consequently, those colours would be seen differently but under whatever names we learn. This issue was discussed under a huge subject called “Personal reality”.
Kindest regards.
