If you are using MATLAB R2014a or earlier versions, you can recolor individual bars by first getting a handles to the bar plot as follows:
bar_handle = bar(ba,'grouped');
Then, access the groups by accessing the children of the handle above:
bar_group = get(bar_handle,'children');
Now, you can decide what colors you want each individual bar to have by giving them a color index and setting the 'FaceVertexCData' property for that group. For instance, if there are n bars in the first group, and you want the first bar to be a different color, you can do:
fvcd = ones(n,1);
fvcd(1) = 3;
set(bar_group{1},'FaceVertexCData',fvcd)
This is not supported in the MATLAB R2014b_Prerelease however.
