I understood that you have a file with 27 sheets (tabs), if yes, just select all the tabs and make the change in the first visible, the others took the formatting applied. To separate them, just click on any tab without being the first one.
Follow this procedure: If the tabs are all in sequence > Click on the 1st tab, press Shift + last desired tab. // If the tabs are not in sequence > Click on the 1st tab, press Ctrl + the desired tabs. Then do the desired formatting on the active tab (anything you do will be replicated to all selected ones), at the end click on any other tab to separate them. (Performed in Win7 + LibO 5.3.5.2)