What does the color of milestones indicate in India?

We are quite familiar with milestones found on the road which conveys or informs of how many distances we have traveled or remaining to be traveled. Milestones indicate not only the distance but also indicate what kind of road we are traveling to. In India, these milestones are divided into different categories. Each has different colors on their head and these colors represent different kinds of roads.

National Highway: Milestone Yellow and White color