I was wondering if anyone else has seen this happen. The lube that I am using, I was told that it was the Paul Matthews formula, but Paul's mix is a lot softer than what I have, I am thinking that it just has more bees wax in it to stiffen it up some. 
I have made up some lube with 3 parts BW, 1 neetsfoot oil and 1 mos and have pan lubed with it and no color change. The older lube I have been using has been run through a luber/sizer and you can see in the pic the color change after a few days. If it means anything, the sizer die is brand new, no left over old lube in it.
Sam

  Hi Sam ;

  I don't think anyone will judge you adversely by the color of your bullet lube. (Hope Not)

  However, we all have our individual preferences and prerogatives and if you would rather have the lube some other color than say "egg shell white", simply make a trip to the nearest five and dime store for a large box of crayons to use as an additive to your existing lube.

  The colored wax crayon/s should not detract from the intended purpose of lubing your firearms bore, and may, just may, improve conditions overall.      

C M M

The Fourth Law of Thermodynamics states:

"Everything eventually turns brown."