Is there any way I can edit armor color? If so ... How ?

You have to alter the Texture file itself. I use GIMP for such things, but Photoshop also works. (any program that can display and edit .dds or .tga files would work I guess)
The files can be found on the CS disk, or by pulling them from your Morrowind BSA.

So do I export the armor files ?

All the files are on the construction set CD, under Data Files.

For simple color changes, I recommend Irfanview.
http://www.zyworld.com/redwoodtreesprite/IrfanView.htm
Be sure to also download and install the complete plugins set, as you can open dds files, a must with some morrowind textures.
And you can use bmps in mods, which is a good way to save your color changed textures.