Blade Color: Red
The Heart of Darkness
Red lightsabers are almost always used by Sith, Dark Jedi, or other nefarious evil-doers. They are designed to be a visual counterpart to the typical blue/green lightsabers wielded by the Light Side Jedi. They represent insidiousness, carnality, and deception.
Red blades are the result of synthetic lightsaber crystals, which emit a distinct energy signature and create a crimson hue — whereas natural crystals emit cooler tones like blue or green.