exr manipulation

[jpaul]

Hello, i downloaded a PBR from the internet. but i want to change the color. in the description of the product it's said it can be done by adding a mask in the composite layers. idk how to do this, and i can rely on GIMP only, as i don't own photoshop. and paint.net doesn't do the trick. so is it possible to do this in GIMP, if yes how? here's the exact descriiption of the pbr so you have a better idea

Material of old painted boards. The color is green by default, it can be changed in Composite Layers using a mask (disabled by default and also not available in FBX)

Thank you