Colombia has several island territories in the Carribean:
Caribbean
Isla Tierra Bomba — a popular resort island just north of Cartagena
Islas del Rosario — one of Colombia's most popular national parks, with beautiful island beaches of the San Bernardo archipelago, and coral reefs that make for great snorkeling
San Andres and Providencia — an archipelago off the coast of Nicaragua with some very fine beach resorts
Pacific
Isla Gorgona — formerly one of the world's most beautiful prisons, the island is now a national park
Isla Malpelo — a remote island nature preserve and a UNESCO World Heritage site, uninhabited save for a small military outpost