Red Color Crystal

The Red Color Crystal can be crafted by players who have taken the Artifice crew skill and reach Artifice Level 80. This crystal can also be bought on the GTN from other players. The schematic to craft it will become automatically available at the Artifice Crew Skill trainer once you reach Artifice Level 80. Artifice Guide

These versions of the Red crystal are available:

• Advanced Red Indestructible Crystal +41 Endurance
• Advanced Red Hawkeye Crystal +41 Power
• Advanced Red Eviscerating Crystal +41 Crit
• Advanced Red War Hero Crystal +41 Mastery (The mastery version can also be bought from the PvP vendor on the fleet, but it costs 200000 credits and require Valor 10. The crafted version does not have a Valor requirement.)

Red Crystal Lore

Traditionally, in Old Republic lore, only Sith use red lightsaber crystals. Red color crystals were almost always synthetically created, as a way to quickly produce color crystals for Sith legions or as a way to avoid the Jedi protecting existing crystal sources. 

Notable Old Republic red lightsaber wielders include Darth Malgus, Darth Revan and Darth Malak.