This latest document of Rigify reads:
Face Bones
Start by identifying basic face landmarks to follow as guide for bones placement.
- Orange lines represent bones that should be placed in closed loops.
- Yellow lines represent bones whose position depends on surrounding bone loops.
- Red lines represent outer edge bones.
- Purple lines represent bridging bones used to cover deforming flesh.
The eyes-nose loop area is split in different parts identified by bone names. Follow the image to place the bones.
What orange lines? Yellow lines? There is not a single picture in this page!
I googled a while and found this link. These pictures should be migrated to the new document.