I don't have a horse in this race (not an ST owner), but I think that I understand why people would want a set of just blue caps.
if you look at the playfield in that area, it's predominately blue with the star map and field underneath them and the blue pop bumper caps fit in perfectly.
that being said, I still think that the 3-color [uniform] package is very nice. maybe offer them in both an "all blue" or 3-color package?