Highlight cell with Fill & Font Colour

nuraisyah,

Do you need to loop?
No loop and conditional format.

Sub tst()
    Dim lastrow As Long, erow As Long
    With Sheets("PO Summary")
        lastrow = .Cells(Rows.Count, 2).End(xlUp).Row
        erow = 4
        With .Range("h" & erow & ":h" & lastrow)
            .FormatConditions.Delete
            .Offset(, 1).Formula = "=(f" & erow & "-g" & erow & ")/f" & erow
            .Formula = "=if(g4<=0,""Insufficient"",""Sufficient"")"
            .FormatConditions.Add Type:=xlExpression, Formula1:="=h" & erow & "=""Insufficient"""
            .FormatConditions(1).Font.Bold = True
            .FormatConditions(1).Font.Color = vbYellow
            .FormatConditions(1).Interior.Color = vbRed
        End With
    End With
End Sub