This technique of coloring mountains in the distance is frequently achieved by varying the opacity of the paint as well as the scale of the mountain on the canvas. One technique for painting distant mountains in watercolor is to make them smaller on the landscape that you're painting. This frequently means that they will be on the horizontal line, but they will also be tiny on the canvas in comparison to larger foreground objects, such as foliage. Larger mountains in the distance are frequently painted with very light washes that resemble faded objects. This simulates the way things dissolve into the distance and works well with mountains.