Aqua is a greenish-blue color, often thought of as the shade of water. When you buy a new blender, you might decide that the aqua one will brighten up your kitchen.
Aqua is pretty close to the color known as cyan, almost exactly halfway between green and blue on the color spectrum. You can buy aqua clothing or aqua paint if you love the color and want your dining room to feel cool and colorful. The word aqua is sometimes also used to mean "water," and in fact the Latin root means "water, the sea, or rain."