any way to batch edit many cells color format?

I read you can change all selected cells to a particular color style you previously created but what I want to do is change each cell NOT to the same style but a particular shade relative to their current color. This sounds impossible without some extra macro or something right?

I have groups of color styles I want to duplicate to just a shade darker or brighter, and the quickest way I can imagine currently is each cell individually. Any ideas? Thanks

Other than Conditional Formatting (which you would have to do manually anyway), you cannot change a cell color with formulas - you would need VBA for that