Considering he posted in the kajukenbo forum, I am guessing he is asking about the significance in that system.dress codes usually mean something but only to that particular style or system. you would have to ask some one that is in the style you saw. some karate only allow white gi. some allow black gi only after a mid level rank like green or brown. some will designate a mix black bottom white top as a chief instructor and a red top as a master instructor. and if you wear a white bedazzled gi trimmed in gold then your elvis. colors it only means something to the person wearing it and their group.
Considering he posted in the kajukenbo forum, I am guessing he is asking about the significance in that system.
To the OP: in my system, instructors are allowed to wear blue/red gi tops, while students have to wear black. I would guess it is similar in kajukenbo.