I have heard conflicting reports about Rainbow Mountain (Vinicunca) . The hike has become extremely popular recently so it has apparently become too crowded and the trail conditions have deteriorated. It is a high altitude hike so you have to be acclimatized. Don't do the hike when it rains (very muddy and slippery and muted colours) or might have snowed. Some people report that the colors did not seem as vivid as they appear in pictures. In tourist brochures the pictures have been photoshopped.
The alternative Rainbow Mountain is also called Palccoyo and it enters the area of the colored mountains through a different access with much less hiking. Hopefully it won't become as popular as Vinicunca.
