How to Merge Custom Styles into Other Excel 2013 Workbooks
Click the name of the workbook that contains the custom styles you want merged into the active workbook and then click OK.
This action closes the Merge Styles dialog box. If the worksheet file that you selected contains custom styles with the same names as the custom styles defined in the active worksheet, Excel displays an alert box that asks whether you want to merge the styles that have the same names.
Click Yes to replace all styles in the active workbook with those that have the same name in the workbook file that you’re copying from. Click No if you don’t want the styles in the active workbook to be overwritten, in which case Excel merges the styles with unique names from the other worksheet.
After merging styles from another open workbook, you can close that workbook by clicking its button on the Windows taskbar and then clicking its Close Window. You can then begin applying the merged custom styles, which now appear in the Custom section at the top of the Cell Styles gallery, to cell selections by clicking their thumbnails in the gallery.