Quality Assurance checks at the lab, aka playing with food coloring and pure strain nasty bacterias.
Each month we have to check to make sure our tray sealer, affectionately named Chewbacca since it makes noises like an angry wookie when lots of samples are pushed through it, works correctly. Hence the colored dye to make sure all the well seal adequately.
Then we have to check our purchased media to make sure it still reacts correctly in the presence of certain bacteria. Mmmmmm mmmmm, nothing like some good old pseusdomonas, klebsiella, and e. coli to have a good time. All in a day’s work, I suppose.