So I recently painted a section of my basement wall with a couple coats of Kilz oil-based stain-blocker primer (Product Page here). The walls are a bright, clean white now.
However, there was a section of wall that I could not access at the time and I had to paint it later. I bought another can of the same Kilz paint, and I had the person at the paint counter spin the can in the spinner to mix it up.
I went straight home and started painting immediately. I figured that since I had just had the can spun at the store, I didn't need to mix it. However, after I finished two coats, I saw that the color was not the same bright white as the rest of the wall - it's more of a cream color.
I doubt that this is simple product variation, because the color difference is pretty obvious even to someone like me who can only name 10 colors or so. Also, the rest of the wall area was painted using several cans of the same Kilz product, but I see no variation there. Also, the underlying wall color is not any different in the new section than the rest of the wall (it was a light blue color).
So my question is - why would this can of paint have different color? Is it because I didn't stir the paint with a stick, even though the paint can had just been put in the spinner at the store not 30 minutes prior?
ok, so this is a case of "user error: replace user". I didn't actually buy the same product. I had used the low-odor oil-based killz primer (green label on the can) initially, and this time I bought the regular oil-based (red label). although the variation is still more than I would have thought, I repainted with the same product and the match is much better.
sorry for wasting everyone's time. I nonetheless learned something from all of the answers.