Each year the Gamblin paint company cleans their filter and makes paint out of the pigment they collect. They put it in a tube and when you buy their paint, you receive a free tube of this random grey paint. The color can be different every year. They call it Torrit Grey. (I believe Torrit is the filtering system.) Also every year Gamblin paint company holds a contest and you can see the rules for yourself at their website: www.gamblincolors.com. There is a link there to see past shows and winners.
Basically you must paint with the current year torrit grey paint and you can use any white and a black.
My Torrit Bird paintings were painted with just the torrit grey and white – Gamblin’s Flake White Replacement.
Even though they allow you to enter 3 works, I only entered the top bird – he was my favorite.