Why is my object pink in Texture Paint mode? The Structural_Material base color image selected in the UV window is the paint slot I'm trying to use. However, I can't paint anything because my model shows up pink. Anyone know why?

Please don't flag this as a duplicate of a question that is completely different, thanks. There are a number of reasons why a texture might be missing to cause something to show up pink in Blender lol.
try to add a image texture node in the node editor then select in the node your chosen image. 

let me know if it works.