I know which ones you mean beaker, just my description leaves a bit to be desired, lol.
I don't mean the background behind the letters is black, just the plastic it is stuck to.
The background behind the letters is still white or yellow, with the petrol effect on the plates.
If you look at yours they'll most likely have the background (yellow/white) with the letters/numbers printed on stuck behind a clear perspex sheet.
The petrol effect ones have the background with the letters etc printed on stuck in front of the perspex sheet (which is black as it doesn't need to be seen through)
Hope i've described it a bit better.