How can I change the default gray color cell fills in Excel?

Question

I want to make the cells have 15% or 10% gray fill instead of the default choices of 25%, 40%, 50% and 80% gray color.

Answer 1

Doesn't look like Excel give us that choice. It is, after all, a spreadsheet program not word processing.

You could copy or cut the file into a Word document. You could keep both copies if you like.

In Word, you would select the cell or cells
cl Format
cl Borders and Shading
cl Shading
Many more choices there, additionally you can click on "more colors" and adjust even more.