Change text colour

[Shaijuzacharia]

I have given the below formula and this gives #NA in columns with no
values. I want to change the font colour to white if the cell has #NA.

=IF(ISERROR(100*(AF5-AH5)/AH5),NA(),100*(AF5-AH5)/AH5)

 

[David Biddulph]

Format/ Conditional Format/ Formula Is:
=ISNA(...cell reference...)
Set font colour to white