Fading

Doctor uncovered the corpse. Just like four others she had seen last few days, it was gray. And not painted gray, its skin, hair, even eyeballs were completely gray.
She made an incision into an abdomen. Like with the outside of the body, the blood and guts were also devoid of color.
"Why does it keep happening?"
There wasn't really much to see what she hasn't seen before. She took her journal and wrote:
"Age: 20, Cause of death: Fading."
It was the 40th young victim of said sickness this year.

Over a thousand years ago, even before the Humans showed up on Urnketh it has been discovered that each of the six Colors get naturally absorbed and stored inside of various parts of the bodies of living beings. Those areas have been named Color Nests. The Nests are needed for the organism to live and if something happens to one of them, the body functions related to it cease.
As years pass and one gets older, Color Nests slowly lose their ability to store the Colors within themselves. It usually only happens when organisms reach their senile years (varies between species), but lately, more and more young people started to contract this condition. The reason why is unknown, but some theorize that it is one of the signs of the upcoming Age of Gray.

Causes

For the most part, it has been considered that fading only shows up naturally with the old age.
But as more and more young people contract it, researchers try to find the cause of their affliction. Right now it hasn't been found.

Symptoms

As the condition progresses gradually, more and more Color Nests start to dissolve, causing more and more body functions to shut off. Depending on which Color is affected those are:

• Blue (located in eyes) - loss of sight and ability to recognize truth and lies.
• Green (located in the throat) - loss of voice and hearing
• White (located around the heart) - increased aggression and impulsiveness
• Black (located in the abdomen) - loss of strength in the upper body
• Red (located in hands) - loss of the ability to perceive danger or paranoia
• Yellow (located in feet) - loss of sense of balance and dizziness

Treatment

Right now, the only cure for the condition is Honey Savior (flower). Eating the flower raw or processing it into a medicine and then taking it stops the progress of fading, however, doing so causes various side effects (depending on the method of eating the flower, the raw being the worst). At best, one will lose the ability to absorb the Colors forever.

Type

Magical

Standard locations of Color Nests within the human body. by Revyera

The Witch that faded

In the last centuries of the Age of War, three Witches showed up, overwhelming all other armies on the battlefields. They were called Three Sisters of War and many of their battles led to many areas of the world being warped today.
As the stories tell, the oldest one disappeared, the middle one was killed, and the youngest of the sisters began to fade, losing the ability to control the Colors. Some think that she may still live somewhere, generating and losing Colors in an endless cycle.

The Grays

It happens very rarely, but sometimes, when a sapient being fades, their bodies don't lose any functions.
These beings, with gray hair and skin are called Grays.
Grays are almost completely emotionless and their bodies start to reject all of the Colors. They are immune to Oversaturation (condition) and the magic but they also can't use magic items that use pigments.
Almost all of them start to hunt warped monsters.