Final answer:
Watercolor is a sensitive painting medium that can be easily damaged. It is traditionally applied to a paper support and relies on the whiteness of the paper for proper reflection of light.
Step-by-step explanation:
Watercolor is the most sensitive of the painting mediums. It reacts to the lightest touch of the artist and can become an over-worked mess in a moment. There are two kinds of watercolor media: transparent, and opaque or gouache. Transparent watercolor operates in a reverse relationship to the other painting mediums. It is traditionally applied to a paper support, and relies on the whiteness of the paper to reflect light back through the applied color (see below), whereas opaque paints (including gouache)