glossary letters - 2nd click interaction

Hey guys, I'm building a simple glossary and I want to highlight the letter that is selected by the user, and when the user clics on another letter "diminish" the first one and highlight the second one. I'm using interactions but I noticed that the 2nd click only works if the user clics the same letter... you can see the issue clear in the snapshot attached. Does anybody knows a workaround for this? Thanks in advance!