This page contains a vector image of the landmarks for MediaPipe Face Mesh that you can zoom into (use pinch to zoom, not ctrl+ / ctrl-) to get a better undestanding of which landmark index is which. Some are very close, if not overlapping. Hover the mouse over the landmark dot to get the index in a hoverText pop-up.
There is nothing special about the different colours; it's just to help differentiate the dots.