You may say "water is transparent," but this is not necessarily true. Color is not a physical phenomenon, it is an illusion happening in our mind. The color of water depends on the context. For example, little air bubbles make water appear white, reflecting sky makes water appear blue, etc.
The Latin word for water is aqua. In the X11 window system this term was introduced to designate the color with RGB coordinates (0, 255, 255), or #00FFFF in hexadecimal. In the print industry the color term corresponding to this RGB value is cyan, thus in the context of computers aqua is a synonym of cyan.
We have to explicitly mention the context, because the term aqua is used also in the printing industry, where it does not refer to cyan but is short for aquamarine. Aquamarine, in turn, does not refer to sea water but to the gemstone of the same name. Its color is more greenish than cyan, in X11 exactly RGB (127, 255, 212) or #7FFFD4 in hexadecimal.
Finally, we can ask the on-line color thesaurus what crowds think aqua looks like. Crowds converge on the RGB value (66, 218, 211) or #42DAD3 in hexadecimal. This is a quite different color.
Returning to the Latin word for water, it remains in the Italian acqua, the Japanese アクア and the German aqua. A propos German, let us look up aqua in the German thesaurus:
Quell des Lebens (umgangssprachlich); blaues Gold; Wasser; das nasse Element (umgangssprachlich); kostbares Nass (umgangssprachlich); H2O (fachsprachlich); Nass
Indeed, wet it is, but it also is precious like gold, it is the blue gold, and it is the source of life.
Water, transparent but of so many different colors. And so precious.