Change the color of the event box based on the selection

I need to change the color of an event box based on the selection done inside the form section.

return "<div id=‘ScheduleEventDetails’


input type=‘radio’ id=‘ExpEventRadio’ name=‘EventRadio’
input type=‘radio’ id=‘RegEventRadio’ name=‘EventRadio’

based on whether the ExpEventRadio or ‘RegEventRadio’ was seleted , I need to give a different color the event box.