Icons allow us to give a visual representation of something functional. When used well, they can make pages easier to scan.
Size & Color
All icons are built on a 16 x 16 artboard. They are adjusted within the artboard based on their desired sized. For anything larger than 16 x 16, an illustration should be used.
Icons are typically a single color. Though some icons have a 50% opacity shade built in for complex visuals, for example:
Use icons at any other size than 16 x 16
Stretch or distort icons