What colour was the Bird of Happiness in the 1908 play by Belgian playwright and poet Maurice Maeterlinck?

"The Blue Bird" is a 1908 play by Belgian playwright and poet Maurice Maeterlinck. It premiered on 30 September 1908 at Konstantin Stanislavski's Moscow Art Theatre, and was presented on Broadway in 1910. The play has been adapted for several films and a TV series.

The story is about a girl called Mytyl and her brother Tyltyl seeking happiness, represented by The Blue Bird of Happiness, aided by the good fairy Bérylune.

Celebrating the 100th anniversary of "Maurice Maeterlinck's greatest contemporary success The Blue Bird", as it was termed, his play was selected as the main motif of a high-value collectors' coin: the Belgian 50 euro Maurice Maeterlinck commemorative coin, minted in 2008.