Inside Bottom of Can Tinted Yellow

 have been an avid Alani drinker for a while, but I have noticed something going on with the bottoms of my cans. It has started to show up in almost every single Alani I can buy, including pink slush (expirations 02/28, 03/28, etc), blue slush (expiration 04/28), dream float can (varied expirations), sherbert (varied expirations), and other flavors too. The bottom of the can it tinted yellow. Not sure why this is happening, whether it is something to do with the can production or the drink itself. I was hoping to get some clarification on why this is happening and whether it is still safe to drink. I have attached some photos of a blue slush can I purchased from Target yesterday with an expiration date of 04/28.