So, I Feel Fine, Yet Earlier Yesterday I Think And

So, I feel fine, yet earlier yesterday I think and today I have black stools which can mean bleeding in the digestive track as I know. However I feel fine, it isn't TARRY, just black, and was wondering what could have caused it. Over the weekend I consumed a lot of pizza and cake with frosting that actually has turned my lips and tongue blue while eating because I would get the frosting on those, was wondering if it could be either of those maybe?