drag an unbound textbox on the detail section of your form.
delete its associated label control.
name the textbox txtHidden. set its Visible property to False.
on the current event of your form, set txtHidden to the value of your PK field in the form.
private sub form_current()
me.txtHidden = me.PKTextBoxControl
end sub
next select all controls on your form (textboxes, comboboxes) and do the Conditional format.
use
Expression: [txtHidden] = [PKTextBoxControl] => choose color you want.
for new record (if you want to set new conditional format)
Expression: [txtHidden] Is Null And [PKTextBoxControl] Is Null => choose color you want.