I had thought that people wrote their own prayers on the flags before stringing them up. But it turns out that the flags are pre-printed, & it looks like every string of flags has basically the same thing on it.
Our guide told us that the flags are always printed in five colors: blue for the sky, white for clouds, red for fire, yellow for the earth, & green for water. I always find it interesting how other cultures perceive colors.
White scarves are also ubiquitous. Our guide greeted us on the first day with white scarves. People drape them around statues of Buddha in the temples. & they add them in to the mix of prayer flags on mountain tops.