In , garfield-n-odie [MVP]
spake thusly:

Spreadsheetdimwit wrote:

I have a spreadsheet which has some cells formatted to change
their fill colour to grey if the letter N is entered. I cannot
figure out how to do this [. . .]

From the Menu: Format / Conditional Formatting...

Set Condition-1 to: Cell Value Equal To ="N"

Or maybe you'll want "Greater Than or Equal To" instead of "Equal To".
Then you can have the cell value *start* with "N" and have it gray,
such as the value "N/A" or "NA", etc.

--
dman