Wht color should i dye the underneath of my hair?

i have medium brown hair and i want a cool bold color to dye the under neath of my hair. i want my hair to look really cool when i put it up so i don't really want a natural color and i really like burgundy but i wont go with my hair color so if you could give me some ideas or websites or something like that please tell em!:) thanks! :)