In the mod folder>>gui>>gfx you can find the textures for the GUI layouts. There is also a folder where Kitya left different choices! Just switch and rename them with the default one.

You can also edit any of them to your liking with any generic image editor that also handles PNG format and transparency like Photoshop

I discovered this because i cant read generic NPC dialogue in the window and was struggling to edit the text color, so here goes the heads up if anyone else has the same problem!

Cheers