How do you mod textures?

I asked a similar question in the 2142 section but Im afraid it wont get seen there so I am asking it here too. I want to make what amounts to chams for bf2 and bf2142. This would be a bright color addition to the texture files in 2142 or Bf2 but I havent found a way to mod these dss files. They are compressed and after opening them I would have to mod them and recompress them and put them in place of the originals. Would love some help with this, if only some hints on the proper software for this. Thanks for any help!!