It is a "color coding" matter so to speak, for the Vdev deviation needed on the RNP AR approaches that some operators do in some parts of the world. This way, when you are monitoring your vertical deviation on a Baro V/NAV profile (this is not the correct terminology, but it is the vertical path on an RNP AR approach), your V/DEV is not displayed magenta, as a constraint would be, but rather green.
I think...
