Mathew, what you're asking for is already possible with just one more line of code:
legend([H.data],'A','B','C') %add legend
Great program. I think the last line should be if(nargout>=1) instead of if(nargout>1).
It seems like the program has at most one output argument. It doesn't make much sense to me to specify two output just to get one out.
In fact, MATLAB throws an exception when I tried to specify an output argument. I guess so far everybody does not need the handles :)
09 Jun 2014
Zip file contains program to make different ternary plots.