The most notable instrument wielded by a Jedi is the lightsaber. Both Jedi and Sith use lightsabers, though the former regard them as a tool, the latter, a weapon. The Jedi's lightsabers emit cool colors, usually blue or green blades (sometimes yellow, or purple, as seen in the case of Mace Windu), while the Sith emit warm colors (red). Lightsabers can be of many different colors depending on the crystal fixture. Most Jedi use naturally formed crystals, whereas Sith tend to use synthetic crystals, which are usually red in color.