Yes, it is possible to count cells based on their color shading in Excel. Here are the steps to do so:

1. Select the range of cells that you want to count.
2. Click on the Home tab in the ribbon.
3. Click on the Conditional Formatting button and select New Rule.
4. In the New Formatting Rule dialog box, select Use a formula to determine which cells to format.
5. In the Format values where this formula is true field, enter the following formula:
   Formula:

   =CELL("color",A1)0 

   (Note: Replace A1 with the top-left cell of your selected range)
6. Click on the Format button and select the color that you want to count.
7. Click OK to close the Format Cells dialog box.
8. Click OK to close the New Formatting Rule dialog box.

Now, the cells with the selected color shading will be highlighted. To count them, use the following formula:

(Note: Replace "range" with the range of cells you want to count, and replace A1 with the top-left cell of that range)

This formula will count the number of cells in the selected range that have color shading.