In the current era, we label the Cartesian plane in x and y as our basis vectors, but what did the Greeks use to label their axis? The Greeks were around long before Descartes, so did they even use the same axis system? Or how did they graph things?
The ancient Greeks did not use rectangular coordinate systems in their mathematics, so it is unclear what are you asking about. The method of coordinates was introduced to mathematics by Descartes.
However the Greeks used spherical coordinates in astronomy and geography, and they labeled the coordinate circles the same way as we do (or more precisely we do the same as they did). I mean equator, ecliptic, meridians etc. In practical astronomy and geography we use the same coordinates as Ptolemy did, with essentially the same names and labels.