Aruba is an island of white sands, blue/green water and frothy waves that offer to visitors a landscape picture-perfect serenity.
Normally the water of sea is uncolored but the color blue that our eyes see is because it reflects the blue sky. From a scientist point of view, this color is produced by a phenomenon called Dispersion which means that the sun light is separated into colors by refraction or diffraction with formation of a spectrum. However, some seas look like green because of wide variety of algae that it posses or gray if there is a cloudy day.
If you visit Aruba, you will never see a gray sea, in contrary, you sure see the most tropical blue/green beaches in the Caribbean.