Half of tongue randomly turns blue, no other symptoms

About two years ago I (22M) was noticing that the right half of my tongue began randomly turning blue. I went to the ER once by I thought it was cyanosis but they told me it was just a bacterial infection. It went on for a few weeks then it went away but today my tongue is blue again and I don’t know why. The only thing I have eaten today is peanut butter toast (definitely not blue), I haven’t brushed my teeth yet and I don’t have any other symptoms. Any ideas of what this could be? https://imgur.com/gallery/blue-tongue-4zIdqgc