Changing Bar Labels
Below is a worked example of changing bar chart labels in Stata:

Please note that it is sometimes more convenient to use value labels rather than graph label options to change graph bar labels. In my example it also allows the legend to be spread over the width of the graph.
The commands used are:
clear all
sysuse auto
label define origin 0 "Europe de l'Ouest" 1 "Asie de l'Est", modify
graph hbar mpg trunk turn, over(foreign) stack name(two,replace)