Frontend Mentor | FAQ Accordion Card

Hi guys! With this challenge I was learning a lot of new for me. As example: making accordion lists, placed two and more backgrounds, make images hidden and etc. But I need your help! I can not to make changed color title of accordion list and overturned arrow icon... Yes. I know

input[type='radio']: checked + "title tag of accordion list" { color: red; }

, but some reason it's doesn't work for me... Will be glad any help! Thanks onyone!