If the Plumey’s/Tuffty's soul-bond with a human is broken, the color received will weaken substantially.

Usually the first color to “tinge” the Plumey’s/Tuffty's soul will affect it the most, resulting in a secondary trait, but not always.

By bonding with a human, their souls can become “tinged” with up to two colors and receive two traits (one secondary and one tertiary). Plumey/Tuffty Bitty souls are always white. Monsters cannot receive the primary trait. There is a small chance (about 10%) that the Monster will receive the secondary trait instead, but there is a much higher chance of the Monster incorporating the negative trait as well. Through life experience and interaction with strong human souls, they can become “tinged” with one color and the listed tertiary trait for that color will likely be adapted into the Monster’s behavior. Other colors may be present in the soul, but they have little to no verifiable impact on the human in question. The primary soul color is the strongest and most prevalent within the soul in question, the secondary soul color is second-most prevalent, and the tertiary soul color is the third-most. Human souls can have one, two, or three main defining colors/traits.

If this doesn’t fit with your view or canon, that’s okay! This details out how I visualize and canonize the souls colors. Plumey Bitties and Tuffty Bitties (c) NanoBanana

Which undertale soul am i