Black and blue, ƒ/10, too -[ HMM ]-

Liquorice imported from Australia. (Yes, it's spelled “licorice” here, but I'm going with the British/Aussie spelling on the package just because.)

 

Using an improvised test pattern, I determined the sweet spot of my Canon EF 100mm 1:2.8L IS USM macro lens to be ƒ/10.

Done