I have seen the same red marking of Wurth Elekronik capacitors. It is irritating as hell since the marking is the negative terminal. The marking goes against centuries old tradition of marking the negative terminal black. The Wurth ones are just standard electrolytic capacitors. It is really confusing at first as the data sheet is a black and white document. At least it does show the marked terminal as being negative. Maybe a new fresh engineer just out of school thought red would be a nice color?
This Mouser number is one I have in stock: 710-865060345007 Wurth refers to them as REDExpert parts although they are just plain vanilla parts.