Colored keys, triple licorice and merengue are some of the most obnoxious game blockers that can make you loose and here's what to use to crush them in the hard levels :
Swedish fish + horizontal striped candy = this will clear the blockers in one go
Color bombing = combining two color bombs is one of my favorite ways to clear any obstacles
Swedish fish + color bomb = this two are enough to clear out remaing blockers
Color bomb + wrapped candy = another fave of mine to clear out jelly /gumball blockers
Color bomb + striped candy = effective combo in clearing out half of the game blockers.