Attack Types

In battle, monsters' attacks are represented by objects of varying colors. These are the Attack Types. Each colored Attack Type corresponds to one of the SOULS of the Eight Humans.

White Attack
White Attacks simply hurt the protagonist if they collide with them. There is no special way to counter them other than avoiding them.

Gray Attack
Gray Attacks are neutral entities that deal no damage and are used for leaving a message. This type of attack is introduced by Napstablook in which it spells out "REALLY NOT FEELIN UP TO IT RIGHT NOW. SORRY.". It is also used by Mettaton EX to spell out "Happy Breaktime!".

Red Attack
Red Attacks do not deal damage under any circumstances. However, they are used to warn of upcoming attacks, usually of which cover the entire area of warning and cannot be dodged unless the SOUL is moved outside of the warning area. When the red attack is used, it marks an area in the shape of a rectangle with a bold border and an exclamation point (!). The bullet then flashes rapidly between yellow and red until the warned attack is used.

The red attack is first used by Ice Cap and is later used by Mad Dummy, Asgore, Photoshop Flowey, Asriel, Mettaton EX, and Sans.

Red is associated with the normal color of the protagonist's and Chara's SOUL. However, the function of the normal SOUL nor the traits associated with the protagonist and Chara reflect the nature of the red attack.

Green Attack
Green Attacks are projectiles that will heal the protagonist, progress the battle in some way, or both. Moving the protagonist's SOUL into them is necessary to end a majority of the fights in which they appear by sparing them. This type of attack is introduced by Vegetoid and is also used by Woshua, Parsnik, Whimsalot, the Royal Guards, and Photoshop Flowey. This attack is also used by Tsunderplane, but its green attack is the only one that doesn't heal the protagonist.

Green is the attack type and color of the Green Human, who is also associated with the Shield Mode and kindness.

Light Blue Attack
Light Blue Attacks, also called Blue Attacks, do not harm the protagonist as long as they are not moving. They are the opposite of an Orange Attack. The mechanic is introduced by Doggo and is used later on by Lesser Dog, Greater Dog, Dogamy and Dogaressa, Gyftrot, Woshua, Papyrus, So Sorry, Mettaton, Asgore, Sans, and the colored laser beams found in Hotland and the CORE. In the Undertale patch, the Blue Attacks use a different shade of blue so it can be easier to see for colorblind people.

Light blue is the color of the light blue human, who is also associated with patience.

Orange Attack
Orange Attacks will not harm the protagonist as long as they are in motion. They are the opposite of a Light Blue Attack. The mechanic first appears with the colored laser beams found in Hotland and the CORE. It is also used in the fights against Pyrope, So Sorry, and Asgore.

Orange is the attack type and color of the Orange Human, who is also associated with bravery.

KARMA
All of Sans' attacks use KARMA (KR). This effect removes invincibility frames, and in turn delays damage input.

Purple is the mode and color of the Purple Human, who is also associated with Trap Mode and perseverance.