Color mask not applied correctly along borders when creating a new asset

[isrRedLabel]

I'm trying to create a new asset (a minibus) and I am encountering a problem with the color mask.

At first, I noticed that around each border between a white area (color variations enabled) and black area (color variations disabled, the windows for example) there are white lines (see picture):



For testing purposes, I proceeded to change the base color of my texture from white to green, and applied a red color variation. It is clearly visible that the color variation isn't applied along the borders:



I also attempted to import the vehicle without a specular mask thinking that could be the problem, but I got the same result:



I checked my textures for issues but the black areas in the color mask are precisely aligned with the areas that should remain a constant color.

I used Blender for the model and gimp for the textures, if it matters.

I should point out that when I am importing the asset using the asset editor, the textures look fine.
Also, I'm not running any mods right now.

I have scoured the internet and didn't find a solution to this. I'm not sure where to go from here, any help would be welcome.

 

[isrRedLabel]

It would appear that the problem was caused by my using a white base color for my texture.

I assume it was due to texture scaling and having an excess of white pixels on the borders.
Changing the base color to grey (45% in my case) solved this issue.