This would be the one about batches and lots, and color differences between paints as the date they were made:
My A-6E intruder calls for Light Ghost Gray and Dark Ghost Grey. I painted as per the kit guide (Testors MM paints) and was surprised at how close these colors were. My Light Ghost Gray was a very old, used bottle, and by the time I finished the project, the bottle was almost empty, and due to its age, soon became a mass of goo in the bottom. I tossed it and bought a replacement on my next trip to the LHS.
I coated the plane with Lacquer Glosscoat (Testors again) as always, and once dry, proceeded to polish it up in prep for decaling. I over-did it a bit and cut though the paint in a couple of spots. No big deal as I have fixed these before. I loaded up the airbrush with paint from the new bottle and I was horrified as the new color was not even close to the older. I ended up re-shooting much of the plane (I used lacquer thinner for spraying hoping this would make the paint adhere better to the clear lacquer beneath).
I should have known better as I have had issues with variations in Testors paints in the past and next time I will start fresh with a new bottle if my existing stock is in question. Spending 3 or 4 dollars would have avoided this aggravation and time lost due to set backs.
Just an experience I just had to share with ya' all.