To change the default background color in Excel, you can follow these steps to set a custom background color for your Excel sheets. However, please note that Excel does not directly allow you to change the default background color for all new workbooks permanently. Instead, you can set a custom background for each workbook or create a template with your desired settings.

Changing Background Color for an Excel Worksheet:

1. Open Excel: Start a new workbook or open an existing one.

2. Select the Cells: If you want to change the background color for the entire sheet, click the square above row numbers and to the left of column letters (this selects all cells). Alternatively, you can select specific cells.

3. Home Tab: Go to the “Home” tab in the ribbon.

4. Fill Color:
   • Locate the “Font” group.
   • Click on the “Fill Color” icon (it looks like a paint bucket).
   • Choose “More Colors” if you want to use the specific color #0D5257 or select a color from the palette.
5. Custom Color:
   • To use the hex code #0D5257 , click on “More Colors.”
   • Go to the “Custom” tab.
   • Enter the RGB values for the color (R: 13, G: 82, B: 87).
   • Click “OK” to apply the color.
6. Saving as a Template (if you want to use this as a default for future workbooks):
   • After setting your desired background and formatting, go to “File.”
   • Click “Save As.”
   • Choose “Excel Template (*.xltx)” from the file type dropdown.
   • Name your template (e.g., “CustomTemplate”) and save it in the default template folder.
   • To use this template in the future, open it from the “New” section in Excel.

Note:

• Each new workbook will still have the default white background unless you open your created template or manually change the background each time.
• There is no global setting in Excel to change the default background color for all new workbooks universally.

If you have any specific needs or further questions about customizing Excel, feel free to ask!