Why wouldn't a format rule of ISTEXT($G$1) won't fill the relevant cells with colour?

[Droriley]

I'm making sure the format is set right and applying it to the left hand column. So why nothing's happening?
If a given answer detailing some basic info about conditional formatting and how it works (what cell to write in formula, how to set what it's applying on etc.) I will be grateful.
File attached.

[Fotis1991]

You were almost there..

Use your formula in CF rules in this way...

=ISNUMBER($G1)

[benishiryo]

hi Droriley, welcome to the forum. you're not supposed to use the double quotes in the formula. you did it right in column H:J. so it's the same under the conditional formatting window. not:
="isnumber($G$1)"

but:
=ISNUMBER(G1)

if you want to highlight H1:I1 based on G1, then you have to put a dollar sign on the left of G1:
=ISNUMBER($G1)
you can try this formula in a cell & copy down/across. you'll notice by copying to the right, it is still comparing to column G. but copying down will ensure G2 is compared instead of G1 again. if you put in 2 dollar signs, you are always comparing to cell G1 no matter which cells is it

and the 2nd one in the Conditional formatting is better. don't refer to the whole range, but just what you need:
=$G$1:$G$20