has participated, has traveled every troupe in the color for her reign for 1955. what does this mean for her, for the royal family? >> reporter: it is the parade which marks the official birthday of the sovereign. and the queen is colonel in chief of trouping the colour, a great honor. it's important that in ceremony is understood. in battle centuries ago, you had the color as a rallying point whereby there was smoke and dust and noise of battle. you could distinguish friend from faux. the last time colors were used were 1881 in the war. subsequently, the color is trouped in front of the sovereign. this has happened every year since 1820, and the sovereign