When using the conditional formatting, all the cells that meet the rules will be in a different color, while other cells will appear as untouched. You can select all cells with conditional formatting by using "Go To Special", please follow the steps below for details:
Step 1: Select the data range;
Step 2: Click the "Home" tab from the Ribbon;
Step 3: Click the "Find&Select" command in the "Editing" section;
Step 4: Click the "Go To Special" command from the drop-down list;
Step 5: In the new window, select "Conditional formatting";
Step 6: Click "OK" at the bottom and the cells with conditional formatting will be selected.