Pick XYZ head mount location; transform those numbers and data

Hi all,
I am trying to collect the location of users in a VR multi presence environment. Basically taking the headsets’ locations on the walking terrain of each user.
In addition, when having the location, add the colour of the terrain that each user is standing on.
Thank collect those coordinates based on colour.

Quite new here therefore, any help much appreciated !

Thank you !

Cheers,
H.