[] = MAKE_CUSTOM_PATCH_LEGEND(colors, labels)
MAKE_CUSTOM_PATCH_LEGEND will plot a custom legend on the current figure.
It uses a hack involving invisible patch objects that I don't understand.
COLORS: either a cell array of n MATLAB color strings ('r', 'b', 'k', etc.);
or a column vector of n scalars, which will index into the current colormap;
or a n x 3 matrix of RGB values for each patch.
LABELS: a cell array of n string labels for your legend.
VARARGIN: name/value arguments to pass to legend().