The sunglasses that have brown lenses can provide with clearer vision than the sunglasses that have grey lenses. I think there isn't anything wrong with the sunglasses. The transition lenses can change into other kind of colors. If you don't like this kind of color, you can ask the optician to find another pair of sunglasses for you. I think most of them will be helpful in this part. Good luck!
If you doubt about the quality of the product, usually you can have a refund within 7 days. But there are brown sunglasses too. They can work the same as grey sunglasses. Is there anything wrong with this kind of lenses? Or you just want a pair of grey lenses? Complain to the manager of the shops and then find what you like. Good luck!
Essilor Transitions lenses exist in gray and brown colors. So your lenses don't have any problems. If you don't like brown color, you can have them replaced as soon as possible. If you want to know more information, you can search online to have a good understanding of this kind of lenses or ask your Eye Care Practitioner about this kind of lenses. Hope this helped!