not sure on the blue cap, it could be a purple, my orange cap is sometimes known as a red cap to some...
I think different people have a different perception of color, and depending on the lights above them as to what color they appear to be, the purple mushrooms that I bought from a local store are blue in my tank and that's not a big issue for me but I wanted the purple LOL
I have blue monti cap. It was light blue when I got it, but now it is more purple, with the polyps being bluish. It probably has a lot to do with lighting.