Lucas Fuel Injector Cleaner Discoloration
 

So I am not sure if this belongs here or in the general forum so mods please move if incorrect placement.

I'm curious if anyone else has noticed this..(I work in a parts store so I see tons of chemicals go through my store each day) On the lucas fuel injector cleaner, the clear bottles where you can see the fluids inside the bottle, the color of the fluid seems to vary. Most times the fluid is clear/yellow but every once in a while we will get a bottle with very dark fluid inside it and I have asked many people what causes this difference. I did an experiment over the last week and put one bottle in a sunny spot in my store and one in a shady spot in the store to see if sunlight was a factor but it is not. Im wondering if the dark coloration is due to an additive that was put in but if that's the case, then why aren't more bottles darker color? Any chemical experts out there that know what I am talking about?
https://www.google.com/search?q=luca...px%3B500%3B500
https://www.google.com/search?q=luca...px%3B500%3B500http://www.ft86club.com/forums/data:...AAAAAAAAAAA//Zhttp://www.ft86club.com/forums/data:...AAAAAAAAAB/9k=

I have customers ask why and personally I would like to know what the difference is.