Homura wears a lot of blue and purple because those are the colors she can be sure of.
Her world is a landscape of muddy browns and olives, punctuated by bright yellows and blues, clear whites and blacks. The blues, she knows, fall across a blue-violet range to normal human eyes. But the gradient of black to brown to gold hides a whole spectrum of colors – scarlet and magenta, orange and rose, turquoise and forest green – that she can't hope to parse, let alone coordinate.
They can do surgery to fix the defect in her heart, but there's no way to put extra sensors in her eyes.
Mami is like a bolt of sunshine, her brown-and-white uniform accented with streamers of yellow. The ribbons she whips out and crafts into muskets are the most vibrant thing Homura has ever seen.
Madoka is moonlight in comparison, subtle and ethereal. To Homura's eyes, the pale yellow on the front of her dress is the only touch of color in a silver-and-white ensemble, tied off with ink-black ribbons. She's a ghost. She's calligraphy.
The first time Homura tries to describe to Madoka how her world looks, Madoka giggles when they get to her out-of-uniform hairbows. "They're bright red! Mama teased me for wanting to be flashy and show off to my secret admirers, and here it turns out you can't see the color at all!"
When Homura wakes in the hospital and opens her hand to find a Soul Gem, the jewel is a dark blue so dull it's almost grey. The uniform it wraps around her looks black-and-white, collar and skirt a similar matte grey with the barest hint of blue.
She wonders if it's really some kind of vivid red and violet. Madoka confirms for her that it isn't. Homura would have liked something prettier, but at least it's not attention-getting in a way she can't perceive.
After a dozen timelines or so, she appreciates it more. It's stark. Professional. She's a soldier, not a figure skater; pretty colors aren't in the job description.
"This must be even more visually confusing for you," says Mami sympathetically, in the middle of the visual cacophony of Charlotte's barrier. "Don't worry, though! I'll keep a close eye out for my junior."
(Madoka isn't here. Madoka hasn't contracted. The silver-and-white vision of her costume is still safely restricted to the realm of her Pretty Cure daydreams.)
"That's not necessary," says Homura, using a Beretta to blow a hole through a Pyotr. "None of the color in here means anything. There aren't important patterns I might miss. If anything, it's easier for me, because having almost everything reduced to shades of brown means I have less meaningless visual data to cope with."
"Of course," laughs Mami, clearly humoring her. "I understand."
Homura stops telling Mami about her vision at all, after that.
After Mami, Sayaka is the brightest of their little core group, her costume almost all rich blues accented with yellow trim. Kyoko, by contrast, has dark grey hair and whips around in a trenchcoat that's nearly jet black. In shadow she blends right in, little flashes of color in the darkness from a bare shoulder, the pale flutter of a skirt frill.
In some timelines, Kyoko stumbles across Yuma, even more of a child than the rest of them but with enough trauma to make a wish worth her while. Her outfit is a lot of white floofs under a dull yellowish-grey vest, with pale-yellow accents to match her hair.
In others, Mami manages to intercept Nagisa, whose brown and light-gold outfit seems to be from the same palette as hers. Homura embarrasses herself only once by saying it's charming that they match. Three weeks later Madoka gets fatally wounded by Patricia; at least resetting the timeline means nobody will remember Homura's flub.
Homura takes off her glasses and sharpens her vision at the beginning of the third or fourth timeline, and then again on every one of the dozens of timelines since.
She doesn't try to unlock the ability to see more colors. How would she know if she'd done it right?
(For that matter, how can normal people tell they share a palette? Mami looks at Madoka's uniform and calls it pink, but maybe if she were suddenly transplanted into Sayaka's body and saw it through Sayaka's eyes, she would start calling it green. Who's to say?)
Walpurgisnacht is always deep-blue-on-black, framed by a halo of pale, sickly light that doesn't seem to penetrate the shadows.
Homura watches her friends bleed out black under that silhouette, over and over and over. As everyone except Madoka shifts in her mind to an obstacle, then to an antagonist, it gets easier to pretend it doesn't hurt to watch.
Then Madoka fills the sky with silver-white arrows, and the universe changes around them.
The two of them float between two vast planes of liquid flowing light. A ring of depthless outer space is visible in the distance, stars and muted nebulae shining against the black.
And the glowing seas of light are full of hues Homura has no words for. Even her own hand in front of her face has changed.
"There are more colors here than any human can distinguish!" says Madoka, clasping a tearful Homura against her chest. "Do you like it, Homura-chan? Since your vision is limited the rest of the time, I thought I would take this chance to give you some colors that nobody else in the world has seen."
"It's beautiful," chokes Homura. She raises one hand to run the fingers through Madoka's impossibly lovely hair. "This...?"
"Oh, that's normal pink! Just because I rewrote the laws of the universe, I didn't change my hair to an impossible color. That would feel like cheating." Madoka tugs free the ribbons holding her twintails, and the hair flows free while she gathers up the fabric and sets it in Homura's cupped palms. "And these are normal red. Keep them, okay? Until we meet again."
Things aren't adding up. Homura's memories. Everyone else's memories. The enemies they're fighting. The size of their little alliance, grown into a full-fledged team with people who shouldn't be alive.
So it's a witch's barrier. How much of it is real?
When Kyoko mentions that she's noticed that the colors are messed up – the green of the trees and the red of her costume are, to her, as inexplicably absent as the faces of their classmates and her knowledge of how exactly she moved here from Kasamino – that should have tipped Homura off as to whose barrier it was.
Homura is tense and confused and frightened. She doesn't know how to cope with this. She's all but forgotten how to cope with reality, now that it's started marching forward through months she hasn't already relived a hundred times or more.
When she starts to see impossible colors blossoming in the landscape, that's what finally reassures her. No matter what's going on with the impossible simulacrum of Madoka inhabiting this world, the real Madoka will be here soon.