Old colour versus fresh new paint.
If still have a old peace of metal with good color quality on it its posseble to let them scan measure the color and get it mixed allmost exact the way it whas in the old time when GM used Ditzler or Dupont colors. A car painting shop nearby will be able to mix it i`ll gues ? The system is named Glasurit RATIO Scan II. Glasurit is the brand name of the paint.
The instrument has proven to be very reliable. If you can not locate the code on your car, or the right shade, you can submit a sample that we can scan and searching out the right paint. The sample can be a part (mirrors, fuel cap, etc.) or a "cut" the size 5x5 cm.
Good luck hunting.