I think so because he said the colors he sees are different and he mix matched the socks and Christmas decorations although I dont understand the calendar thing
I think the calander thing has to do with the fact that some calanders mark holidays and such with red text and not black. If you're completely colourblind then the red will look gray, and since grey and black are very similar they can get mistakes for each other. So the completely colourblind person will not be able to easily differentiate holidays from regular days.
Although I don't think ren is completely colourblind, cuz he can see blue, so I think that bit of information is not really relevant to him.
Ya I assumed it was red green colorblindness from the Christmas decorations but if thats the case it still may explain the not being able to see the red matked calendar dates
Ren has colour blindness or something?!