The codes for B&W and color (at least for Kodak films) are pretty different. The code is also illustrated on the box (again, Kodak products, Ilford too, I believe) so you can look at what to expect before turning out the lights.
As sort of a last resort short of turning on the lights on a sheet, put the sheet over a card or piece of paper and trace the notches with a thin lead pencil, then put the sheet back in the holder.