Variable color change

Can someone explain when I create 2 variables (width and height), that the program will change them to a Purple (Sensing) block. I’ve noticed that if I have two variables that have similar name (Width/width), but are differentiated by a capital letter that both variables will not change to purple.

VEX_V5_Purple_Variable

It appears to me that they turn purple when in an assignment block. Also, this doesn’t appear to have anything to do with VexCode. Please move this into the appropriate category.