Each User Groups is assigned a color on the CR. When you look at the listing of who is online at the bottom of the main page of the CR, you will see who is currently online. The crest, which varies according to the group, under your name corresponds to your group color.

Administrators = deep red
Den Leader Prefects = green
Special Project Division Prefect = green
Jr. Prefect = green
Prefect in Charge = lime green
Prefect in Charge in Training (PiCiT) = lime green
Gryffindor Professors = pink
First Years = silver grey
Second Years = orange
Third Years = bright blue
Fourth years = fuchsia (bright pink)
Fifth Years = bright red
Sixth Years = medium pink
Seventh Years = maroon
House Creature/House Guardian = purple
CR Moderator = powder blue
Gryffindor Librarian = gold
Guests = peach
Quidditch Captain = silver blue
HOL Head Office = dark blue
Validating = black