I never really had a problem with the Cage uniforms later on in life, but when I was very young and TOS was all there was, I think I found the colors of the tunics very...well...boring. I didn't realize The Cage was even a thing until I saw Menagerie, and had already been "spoiled" by the bright, brilliant primary colors of the production series. Not a big deal now that Trek has a long history and diversity of costume design under its belt, but I found Cage uniforms quite "meh" back then...at least until TMP uniforms came along. 
