All I do to get colored speculars is turning them from greyscale to rgb 32-bit and make completely black alpha channel (at the time tga is saved as rgb 32-bit, photoshop automatically creates white alpha channel - now I'm sure it doesn't work in BC anyway but I like to keep it black

) then it's up to you what you want in color and what not;)
You can always just copy your diffuse map and rename it from _glow to _specular, open specular, clear alpha channel and then play with levels, exposure, contrast, brightness etc. etc. to make nice speculars (drawback is that colors will become really harsh for your eyes so I recommend lowering saturation considerably ;) )