Sure, I can help you with that! Here's how you can make a cell filled with color more transparent in Excel 2003:

1. Select the cell or range of cells that you want to change the transparency of.
2. Right-click on the selected cells and choose "Format Cells" from the context menu.
3. In the "Format Cells" dialog box, click on the "Patterns" tab.
4. Under "Background Color," select the color that you want to make more transparent.
5. Click on the "Custom" button at the bottom of the dialog box.
6. In the "Custom Colors" dialog box, adjust the "Transparency" slider to the desired level of transparency.
7. Click "OK" to close the "Custom Colors" dialog box.
8. Click "OK" again to close the "Format Cells" dialog box.

Your selected cells should now be filled with a lighter shade of the same color as your column heading. If you want to adjust the transparency further, simply repeat the steps above and adjust the "Transparency" slider as needed.