This is what happens when your SOUL is harvested by RW Sans. Colors of outline vary, depending on, usually, your main color. Sometimes, SOUL power. The only reason SwapFell Sans is pink is because he was infected BEFORE he was harvested. Usually, they have SOULs in front of them, but SwapFell does not. Usually, some parts of the SOUL is black, being infected by HATRED. Here's a picture.

Enjoy!