Acrylic Paint
Acrylics are water-based, which means they can (and should) be mixed with water. 🙂 Mixing acrylic paint with water obviously thins the paint, but the biggest advantage is the cleaning process.  You can use soap and water, instead of toxic paint thinners or other chemicals, and clean your brush set much faster than oils.
Acrylic paint is manufactured using pigments that are mixed with emulsions and acrylic resin. This type of paint is super fast drying and is often used in thin, watery glazes as well.