After pumping this morning I noticed my milk from each side is different colours. Why is this so? Is it normal?

Milk on the left may have more colostrum. The breast produces colostrum full of antibodies when baby is sick and baby's saliva touched the breast. At times, it is due to mummy's diet or one side have more fore milk/hind milk. They are of different color. If you are concern, you can ask the doctor during your next visit.