How long have you owned the truck?
From the description it kind of sounds like somebody may have put block sealer in it, and now it is getting stirred up and coming out.
One of them has a red color if I recall correctly, maybe k&w?
They definitely have a distinct smell, I find the reddish color and smell a dead give away.
Edit Note: Napa, and others I'm sure, sell a tester for head gaskets. Its a plastic tube affair with a suction bulb at the top. You put some of the supplied liquid in it and if it changes from a blue color to a yellow then combustion gasses are present in the coolant. I think its like $20 or so, another testing option.