I'll admit that when I got the Vitamin C, I did not see the instructions that I should keep it refrigerated until use. As a result, when I opened the Vitamin C serum, it was already starting to turn yellow, slightly lighter than what the picture captures. And also due to the color change, I may not see the results from it. While I understand that Vitamin C is not the easiest to formulate, I would expect to at least not oxidize before I can open the product, refrigerated or otherwise. Alas, I do not have a way to keep it in my fridge if I ever repurchased this so I question the stability of the formula itself. Not a product for me unfortunately.