Conditional format entire column

[PAB1020]

My first post for help here.
I'm not a novice nor am I an expert.
I don't have a problem returning error message (with #DIV/0!) but I want it formatted with red font (not that the format matters).
I can get it to work - one cell at a time, but for 35 rows - gotta be a better way.
Formula is true: =ISERROR($I$31) Applies to =($1$31)
I want this top apply to all of Column I - I4:I36
Tried =ISERROR($I$4:$I36) - Applies to $I$4:$I36 - doesn't work, font stays black.

 

[Fluff]

That should eliminate the div0 error you asked for, assuming that H6 is 0 rather than blank.