Chromas

Chromas is a rare type of magic amongst monsters that allows them to use different types of magic related to the seven Soul Traits. This magic is so powerful it puts them on par with human wizards. The way it manifests varies; for example, Gaster summons up to seven hands each with a hole in the center, and the color of the chroma he uses will fill the hole.

Red
The red chroma usually takes them form of lasers or energy blasts.
 * Gaster's red hands shoot out laser beams
 * Chara's knife release commanded and uncommanded magic slashes, a magic wall, and make the ground explode.
 * HATE's arm-mounted blade turn red, and when these are stabbed into the ground, it makes the ground explode like Chara. They can also summon a big red sword

Orange
The orange chroma tends to be destructive.
 * Gaster's orange hand creates small white orbs that when triggered turn orange and release powerful explosions.
 * Chara's knife can release a magic slash that can change direction mid-attack.
 * HATE can turn it's claws dark orange and can explode on command.

Yellow
The yellow chroma tends to focus on a ranged attack.
 * Gaster's yellow hand rapid fires small bullets.
 * Chara's knife fires a laser, the size and power depends on how long he charges it.
 * HATE can turn it's claws dark yellow and fire powerful bullets.

Green
The green chroma is used for defensive purposes.
 * Gaster's green hand summons a shield or dome to block attacks.
 * Chara's knife generates a small shield.
 * HATE can possibly turn it's claws dark green or make a dark green aura and make some sort of shield, due to it never changing it's claws green in a way.

Cyan
The cyan chroma focuses on creating strings/ropes.
 * Gaster's cyan hand will fire up to multiple ropes at the target, one from each finger.
 * Chara's knife shoots on large rope out.
 * HATE's claws turn into a dark cyan (teal or turquoise), but it forms into a nub while a dark cyan tentacle comes out.

Blue
This chroma is very versatile, much like it's associated trait. Though all of the uses demonstrated show a blade of some sort.
 * Gaster's blue hand fires up to two circular razor blades per hand.
 * Chara's knife drastically increases in length and glows blue.
 * HATE's uses a dark blue wavy energy that creates a aura that can detect Soul's and turn them blue like Sans, Papyrus and Gaster. Also they can create a dark blue platform that HATE punches, which sends Chara flying.

Purple
This chroma, like it's associated trait, focuses on slow healing and defense breaching.
 * Gaster's purple hand shoots out a purple spike that induces slow healing.
 * In Yet Darker, due to the void messing with his magic, the purple hand will instead copy his opponents attacks.
 * This is because if both of Gaster's sons are alive, his purple hand is unavailable.
 * Chara's knife releases three purple slashes that will destroy the first thing it collides with and will then function like a a normal slash.
 * HATE's claws turn dark purple and can do a powerful slash with it's said claws.

Trivia

 * Though Chara in season 1 uses something very similar to chromas magic, it is unknown if he is actually using it.
 * It is also unknown if his black blade would be considered a "chroma".
 * If Gaster's children are alive, he can only summon six hands.
 * Due to Gaster being born having holes in his actual hands, he can use his chromas from them without having to summon more.


 * It's unknown if all monster-related chroma works the same.