Texture Colors

I want to change the color on a texture using GIMP. I'm finding the part of the texture I want to change is "colorless" or its not being acknowledged as a color. I'm assuming the original creator some how made it that way because the shader was used to change that part in Unity but I'm no longer using that shader so I thought I would change it in GIMP. Can someone explain the "colorless" part of the texture? It doesn't respond to hue saturation.

 

Is it transparent, maybe? There's no such thing as "colorless", as far as I know.

What is file format?

 

Its png.
If you look at these pictures it will make more sense. In this example I just changed the hue saturation to show how there is one area that is not effected, thats the area I need to change. Can you explain this?

 

I'm not sure how Gimp handles gray-scale colors when adjusting hue and saturation. What happens when you adjust the color balance? Does that add color to the gray areas?

 

Yes adjusting the color balance does add to the gray areas. Thanks I think I can go with that, the tutorial I followed used hue saturation.