Northstar (2nd of 4)
This is the first actual costume of Northstar. His twin sister Aurora had a similar costume, though her star was on her right hip. When standing next to each other, the stars on the twins‘ hips connected into one image - a symbol of their shared power to generate brilliant light. [Uncanny X-Men #121]
Northstar (3rd of 4)
Although most of his teammates changed their looks over time, Jean-Paul stuck with his costume until Alpha Flight adopted a team look, all wearing the same red and white armor with a maple leaf symbol on their chests. [Alpha Flight (1st series) #103]
When the Canadian government disbanded Alpha Flight, Northstar returned to his classic black and white look. Even later on, when he affiliated again with a re-organized Alpha Flight, he stuck to it. [Northstar #1]
Banshee originally wore a formfitting green suit with a yellow triangle in front that became a high collar in the back. He wore matching tight yellow gloves and boots. What kind of became the signature of his costume though were the black and yellow winglike stripes, connecting the arms to his hips. They made it easier for him to fly. [Uncanny X-Men #28]
Banshee (2nd of 4)
When the Reavers attacked Muir Island, Banshee wore the basic blue and yellow training outfit of the X-Men. A couple of days later, Moira MacTaggert designed new body suits that were an updated version of the classic X-Men costume, including body armor and other special functions. Banshees’ costume was once again equipped with the stripes. [Uncanny X-Men #255, 258]
Right before founding Generation X, Banshee briefly returned to wearing his classic green costume. [Uncanny X-Men #316]
Banshee (3rd of 4)
As headmaster of Generation X, Sean rarely used a costume at all, but wore average streetclothes. Only when training with his young charges, he went back to his modified blue and gold standard X-Men look. Much like the rest of the team, Sean wore clunkier boots and, occasionally, switched to a similar outfit without the striped wings, often wearing a jacket over the suit. [Generation X #4, 16, 18]
MYSTIQUE
The first variation of Mystique’s standard uniform: a white bodysuit and long skirt slit to the waist on each side, held by straps on each side, which made it unclear whether one saw skin at the sides or a blue-black bodysuit underneath. The skull belt was not only decoration. Actually, the skulls were small weapons or other devices which Mystique could shift back to their proper form whenever she wished to use them. The overall impression was mysterious and threatening. [Ms. Marvel #18]
Mystique later switched costumes to a slight variation of this outfit: instead of straps at the side, the white leotard was covering her sides and the skirt was somewhat shorter. It was also clearer that she wore a black suit underneath. This became her default costume to which she always returned in-between other costumes. [Uncanny X-Men #177]
Later on, Mystique used a third variation, the sides of the white dress again being open, but no longer held by any straps. Otherwise, the uniform was the same. [Uncanny X-Men #266]
When Mystique was pressed into service by X-Factor, she first wore some basic black bodysuit with a few white elements (shoulder area, boots). [X-Factor #112]
Soon, she switched to another uniform. A bodice, short jacket and thigh-high heeled boots held by red straps in combination with a red weapons’ belt. The outfit first seemed to be made of black leather but was quickly exchanged for a white version. Mystique’s hair was also wilder and longer at the time. The impression was both sexier and – fitting with X-Factor – more militant. [X-Factor #114-115]
Her next X-Factor outfit was once more a bodysuit in her typical color scheme, reminiscent of her standard costume but without the skulls, the skirt or any other obvious weaponry since, at the time, Mystique used her shape-changing powers more aggressively.
When Mystique broke free from the X-Factor, she alternated between several of the costumes she had worn before. [Uncanny X-Men #359, X-Men (2nd series) #93]