If you dont have photoshop to colour the models, dont worry, there are some dds converters around.
http://www.vcbase.com/downloads/tools/ddscv_1_20.zipso use them to convert the specified textures to jpeg, and colour them with paint for example: VC red 255, and US Blue 255.
then convert back to dds.
but dont forget you need to pack it as a .cbf, placed in addons.
you can also create an object in 3d max, and apply the textures on the objects.
now open up a specified map in the editor,
duplicate one, or open the extracted levels)
and put the .bes below the terrain, or in the air, just make it really small, or change the LOD so u wont see it.
dont forget to add the textures to vietcong/levels/theduplicatedmap/TEX.
then repack the map into an addon, and if vc loads the map, it will automaticly overwrite objects+textures with the same name.
remember both require to be repacked as an addon, so you need some sort of .CBF creator.
you can use this for the demo, and just replace the textures, since it doesnt requires to be repacked.