- Queen Elizabeth II has become Britain's longest-reigning monarch
- Almost 1,500 officers and men took part, with 200 horses and over 400 musicians.
London (CNN)At 90, Queen Elizabeth II is getting bolder.
In grand celebrations to mark her milestone birthday, the Queen on Saturday sported a daring neon green outfit as she greeted the public, impossible to miss in her horse and open carriage, even past the thousands of viewers and hundreds of marching officers.
Celebrations began with the traditional Trooping the Color, a spectacular display of more than 1,400 officers and men in their famous red jackets and black bearskin hats, with 200 horses and more than 400 musicians.