SOUL Modes

In battle, the protagonist is represented by their Soul: a red heart. However, many bosses in the game can alter the color and change the way it behaves. These are the Soul Modes.

Each Soul Mode corresponds to one of the Souls of the Eight Humans.

Red


While the Soul is red, it is in Normal Mode and behaves normally. It can move in any direction at a constant speed as if the player is in a top-down perspective, and can slow down by holding [X] or Shift. The Soul's heart sprouts legs when it runs away from battle.

Red is the true mode and color of the Souls of Frisk, the Eighth Human and the player character, and Chara, the First Human, and their Determination.

Blue


When blue, the Soul is in Jump Mode and affected by gravity, much like a side-scrolling/platformer perspective. This is used by both  Papyrus  and  Sans  in battle and is the first time you see the Soul change color. Sans appears to have much more control over this, being able to force gravity in all four directions rather than just straight down.

Pressing a direction opposite to the force of gravity causes the Soul to "jump" in that direction. The height of the jump is dependent on how long you hold the direction up until you reach the max height, which can depend on the attack. In fact, near the end of Papyrus's final attack, the max height is so great that holding the jump can cause the Soul to rise beyond the battle box, even causing the box to extend upward to make room.

Blue is the mode and color of the Blue Human, who is also associated with ballet, dancing, hopping, jumping, twirling, rhythm, and music.

Green


While green, the Soul is in Shield Mode and cannot move. Rather, you control a shield-like spear from Undyne that protects the direction you press. Instead of dodging a pattern, the player must block arrows coming in from all four directions using this spear. This is used by Undyne, who switches the Soul between green and red using her spear. Also, it is impossible to flee in this mode. Undyne gave the spear in an attempt to force the human to face danger head-on.

Green is the mode and color of the Green Human, who is also associated with Green Attacks, shielding, frying pans, cooking, healing, and kindness.

Purple


When purple, the Soul is in Trap Mode and can only move freely left and right on a line or switch between lines using up and down. Spiders move on these lines that the player has to dodge, acting like a web. This is used by Muffet after she fills the Bullet Board with purple liquid.

Purple is the mode and color of the Purple Human, who is also associated with traps, note taking, problem solving, analysis, intellect, perseverance, poison, and Karmic Retribution.

Yellow


While Yellow, the Soul is in Shooter Mode and is flipped upside down so its heart's point is directed toward the foe. Pressing [Z] shoots a projectile that can destroy certain oncoming projectiles or set off bombs, as well as damage the enemy in certain situations. This happens after the player presses a button on the phone Alphys gives you, and is only used against Mettaton and Mettaton EX, as well as the Lost Soul variation of Alphys.

Yellow is the mode and color of the Yellow Human, who is also associated with guns, bullets, sharpshooting, accuracy, and justice.