For it to work in multiple colors, you make sure your x and y are produced with/as meshgrid. Also specify your colors according to your choice of colorbar. Eg if your caxis ([15 30]) for SST, then you should have the function as:
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 :)