Excel saves custom Styles in the workbook where they were created and saved.
To use the Styles in a different workbook, either copy the custom Styles by merging them, or copy the Styles from one workbook to another.
To merge Styles:
1. Open a new workbook.
2. Select a cell, Select Home -> Cell Styles (in Styles Group) -> Merge Styles.
3. In the Merge Styles dialog box, select the workbook where the Styles to merge were saved,
and then click OK.
4. In the Style dialog box, click OK.
The merge Styles are presented at the top of Cell Styles palette under Custom.