Chrometale (also called Monochrome Tale) is an Undertale AU that alters all main and secondary character appearances and personalities.
In Chrometale, when Frisk falls into the Underground, they find that all inhabitants are grey and haunted in appearance, and that they have dull, hopeless personalities. As each character interacts with the protagonist, they slowly gain color and develop personalities similar to the ones they had in the original storyline.
As the story progresses along the Neutral route, it is revealed that all the inhabitants of the Underground are already dead, and that Frisk's arrival has reminded them of the way they were when they were alive. The only character who was aware of this, due to being a ghost already himself, was Napstablook. Everyone else believed themselves to be alive, and did not remember their deaths or anything before them.
There are not yet storylines for the Genocide, Pacifist, and True Pacifist routes.
Frisk is the protagonist as in the original story, but has subtle design differences. First of all, they are older, almost a teenager, suggesting that this story takes place after one of the original Undertale routes, though that is not confirmed. They have color unlike the monsters, and though the hair and clothing designs are the same as the original, their eyes are golden.
Chara also has color, but instead of the often pictured red eyes, has blue. Chara also seems to be a bit older than the original design.
Sans and Papyrus both start out monochrome and depressed, with perpetual frowns and blank eyes instead of their usual grins, but gain the cheer and energy of their original characters after interacting with Frisk.
No other characters have been introduced as of yet. This article is still incomplete.