to add textures, get the bit you want and give it a material name the material in the links section of the weapon, where it shows the colour preview, usually of a sphere in the bit that says MA:material.001 or whetver. Change that to black75 or red or whatever you are using and when you export it, you need to have a 16x16 png named red or whatever you called it in the folder and zip with the weapon.
