@swilde Thanks for your comments. The red blob is a marker on the tree to indicate which mountain trail one is following. Our Alpine guide - the one with the red t-shirt - explained that all the regular trails are marked and mapped out for the safety of trekkers so that they do not get lost and also so that could be easily found and assisted if they find themselves in trouble. They just have to indicate which colour code they have been following.
Thank you for the fav. Much appreciated.