Can Countifs and Sumproduct work together?

I have a column I4:I80. In this column, all the cells have either text "NF" or "F". Some of these cells are coloured light grey and some are not. I want to have a formula that will count the number of NF or F that are only in the light grey cells.

This is the formula I used for counting the number of "F" :

=countifs(I4:I80,"=F", I4:I80,"=sumproduct(--(colorindex(I4:I80)=colorindex(I87)))")

I87 is the cell where I have the light grey colour.

Why does the formula return a 0 (zero) for both NF and F? (I have 20 NF and 8 F in light grey coloured cells.)

Can anyone help? Thank you.