The w3-border class adds a border to an element. The default border-color is gray.
Red border
Pink border
Purple border
Deep-purple border
Indigo border
Blue border
Light-blue border
Cyan border
Aqua border
Teal border
Green border
Light-green border
Lime border
Sand border
Khaki border
Yellow border
Amber border
Orange border
Deep-orange border
Blue-grey border
Light-grey border
Dark-grey border
Black border