These are Buddhist Prayers and the stone are called Mani Stones. What is see inscribed (painted) on these stones is the mantra in Tibetan with the six syllables colored.

It reads "Om mani padme hum".

Picture taken at a village near Sangla, Himachal Pradesh, India.

Read more about it at https://en.wikipedia.org/wiki/Om_mani_padme_hum