Brittany is very similar to Alvin: They are the leaders of their respective groups, very competitive, enjoy extracurricular activities, often the most outspoken, stubborn, arrogant, selfish and conceited. Their unwise decisions or "spotlight" personalities commonly are the cause of many mishaps and adventures. Despite their selfish interests, they usually come through for their siblings in the end.
Brittany "hates" green (as stated in Cinderella? Cinderella!) and never really takes the time to realize her younger sister Eleanor wears green. However, Eleanor doesn't seem to be offended by this statement. Though she could mean she doesn't look good in green.
She also hates black. In the 80s episode The Greatest Show-Offs on Earth, Alvin tells everyone to wear black to avoid being spotted, but Brittany refuses to instead dresses in a pink superhero costume. In the CGI episode Albrittina, Brittany does admit she doesn't look bad in black.
Brittany is nyctophobic or afraid of the dark.
Brittany is the only member of The Chipettes who kept her original eye color in all versions.
In an interview, Janice Karman explained the origin of the name "Brittany" stating "Well this was way before Britney Spears or any other Brittany I ever heard of. We had a singer in the studio and that was her name, so that’s why I named her Brittany because I liked the name."[1]