Your paint man is telling you that there are 5 shades of L90E if your confident that your Petrol filler cap is the same colour as the rest of the car, polish it, remove it, and take it to your paint man, he can the cross reference L90E with the 5 different shaded colour chips, No1 shade of Alpine white, was always a good match.
Your paint code only tells you the name of the colour, and not the shade!
Thom