Dichromatic
The first time Danny Fenton died, the world turned gray.
The toxic green faded to blazing whites as Danny's screams faded into the hum of the portal, and Sam and Tucker knew.
Their best friend— their soulmate— was dead.
And it was their fault.
They clung to each other, Tucker sobbing, Sam quietly crying, unable to tear their eyes away from the monstrosity that had taken their friend.
And then a hand emerged from the portal, clutching the side.
They both screamed, clinging to each other tighter, pulling each other away from the portal as a figure as black and white and gray as their surroundings emerged from it, stumbling against its side.
"Wha..."
Then the figure collapsed. Bright rings of light formed around it, splitting in two. And as they split, color returned to the world.
"DANNY!"
*~*~*
After the accident, colors were never the same for the trio.
Sam noticed it first. Tucker's beret seemed a bit less vibrant than it had been before, and his shirt a little more green. The purple she had loved now seemed more blue than purple now, and white light took on a light blue hue.
When she admitted this to Tucker, he told her that colors had changed for him, but in a different way. Sam's trademark purple seemed more red to him, not blue. His own clothes seemed the same to him, but Danny's blue eyes seemed more green than they had been before, and the white light of school seemed more yellow.
They both agreed on one thing, though. Green had become a much more vivid color for them both.
When they talked to Danny about it, he seemed surprised and offput, but also a little relieved. He had thought the color changes were just him. But unlike his friends, green had dimmed in vibrancy for him. Tucker's yellow sweaters seemed more red to him, and but for the green in her skirt, Sam's outfit remained unchanged. The white of Danny's shirt, however, took on a magenta hue.
It was Tucker who connected the dots, and only then after learning about the primary colors of light in science. The diagram made everything click: Sam had lost some of the red in her vision, making purples seem more blue, and yellows seem more green, and whites seem light blue. Tucker had lost some of the blue in his, making purples seem more red, and light blues seem more green, and whites seem more yellow. And Danny had lost some of the green in his vision, making yellows seem more red, light blues seem more blue, and whites seem more magenta.
When he excitedly told Sam and Danny about what he'd learned, Sam was fascinated, and Danny relieved. They didn't have an explanation, but they could identify a pattern. And that was better than nothing.
*~*~*
The first time Danny went ghost, the colors the Sam and Tucker were missing to some extent shut down completely.
Tucker's world became a wash of blues and blue-greens and pinks and reds; Sam's a mix of blues and golds and browns.
Danny, however, had a completely different experience. Rather than the blues and tans of deuteranopia, he saw the world in vivid greens. Green stained the sky and colored the ground below. Yellow greens made up the humans and animals he saw; blue greens dominated the ghosts.
The trio could only stare at the world around them, and then at each other, when the world changed color with the flash of Danny's rings of light.
It was then that they knew their world would never be the same again.