The costume designer usually details the exact colour desired for the costumes in their sketches. Fabric dyeing is a meticulous art that is practised in a proper laboratory of colours. Each colour is mixed specially.
Most of the time, the fabrics are dyed before being cut. That way, they do not need to be soaked again, thus avoiding any possible shrinkage.
It takes about one and a half hours to dye a fabric and for the colour to set. It is then air-dried to avoid it becoming creased or damaged.
The workshop also creates patinas (ageing effects), fake bloodstains, wine stains, etc. The visual test takes place onstage. The effects are observed under the stage lights.
Dying and patina work is something you have to feel, you cannot learn it at school. L.A., head of the Dyeing Workshop
For a long time, people avoided wearing green in theatres and operas, believing that the colour brought bad luck. That belief is directly connected to the art of dyeing. In the sixteenth century, to make costumes green, they were painted with a pigment obtained by oxidising fragments of copper with lemon (or urine!) and vinegar. The mixture gave the costumes a magnificent shade of green but proved extremely toxic for the people who wore them!
Superstitions relating to colours have varied depending on the era but also on the country or region. In the United Kingdom, blue was avoided, in Spain, yellow, and in Italy, purple.