Hi: It depends partly on how you are creating your bar charts: SAS/GRAPH or ODS GRAPHICS. And, what kind of template? A style template or a graph template? Generally, grouped data is given colors by the GDATA1-GDATA12 style elements in a style template. If you change the colors in the style template, then the style template colors will be used unless you have other overriding statements. I have an example of changing bar chart colors in the paper: https://support.sas.com/resources/papers/proceedings10/033-2010.pdf
But there are other ways to change the color, too. If you always want one group to be red and the other group to be blue and, if you are using ODS GRAPHICS, then an attribute map is another way to change colors based on a group value. It really depends on how you are creating the graphs.