Kyber Crystal

A lightsaber crystal was a term used to describe any variety of crystals, gems, stones, or other objects used as the focus in the construction of a lightsaber.

At the heart of every lightsaber was a set of crystals that resonated to produce the efficient, powerful blade. While the most common crystals used in the process were from the Adega system, Ilum, and Dantooine (in the so-called "Crystal Cave"), Jedi and Sith used a variety of crystals to produce various colors, effects and unique abilities. Some crystals could even enhance the Force skills of a particular user. Other gems, such as colored crystals or diamonds, were used exclusively for prismatic effects. However not all lightsaber crystals were actually crystals at all. There were plenty of exceptions where a Jedi or Sith would use a different material or substance in place of a crystal, such as physical remains, shards of glass, and even special micro machinery.

Preparation
Before placing the crystal in the lightsaber, the Force-user had to imbue them with the Force. To do this, the Force-user was required to meditate on the crystal for many days, depending on the user's connection to the force. While the Jedi used natural crystals, the Sith mostly used red-hued synthetic crystals. Sith-made synthetic crystals created a slightly more powerful blade when energized by the dark side of the Force. Sith lightsaber blades could "break" the blade of a Jedi Saber, but such occurrences were rare.

Significance of colors
Lightsaber crystals are used to indicate a Jedi's chosen class. Blue indicates a Jedi Guardian, a Jedi who used the Force on a more physical level. Green indicates a Jedi Consular, a Jedi who preferred to reflect on the mysteries of the Force and fight the dark side at its heart. Yellow indicates a Jedi Sentinel, a Jedi who honed his or her skills in a balance of combat and scholarly pursuits.

Jedi Exclusive: (Can also be used by Jedi turned Grey Jedi)

 * Blue: Indicates the lightsaber of a Jedi Guardian. This is a Jedi who tended to fight the Sith on a physical level.
 * Dark Blue: Stronger user of the force
 * Light Blue: Training saber
 * Green: Indicates the lightsaber of a Jedi Consular. This is a Jedi who preferred to ponder the mysteries of the force and fight the dark side at it's heart.
 * Dark Green: Stronger user of the force
 * Light Green: Training saber
 * Yellow: Indicates the lightsaber of a Jedi Sentinel. This is a Jedi who honed their skills in a balance of combat and scholarly pursuits.
 * Dark yellow: Stronger user of the force
 * Light Yellow: Training saber
 * Teal: Indicates the lightsaber of a Jedi Healer. This is a Jedi who practiced great devotion, trustworthiness, and healing.
 * Emerald: This was generally used by an observer of the Force. Generally this person attempted to avoid combat and simply study the uses of the Force by watching others.
 * Bronze: This indicates the lightsaber of a Jedi who has mastered control over their anger above all else. It has been used in past times by wookie Jedi who have overcome their anger towards their enemies.
 * Gold: This lightsaber is generally used in the ceremony of granting a Jedi the rank of Jedi Master or High Master. (Jedi Grand Master only) This lightsaber is owned by the Jedi Grand Master.

Sith Exclusive:

 * Red: Indicates the lightsaber of a Sith or Dark Jedi. This is a characteristic that generally indicated a prominent user of the dark side of the force. The red represents blood and violence. Generally these crystals are synthetically grown.
 * Dark Red: Stronger user of the force
 * Black: A virtually impossible beam to create, the black lightsaber is convented by all dark side users. It is only a legend that such a crystal exists that would allow a dark side user to create such a beam. It's powers, unknown. (Sith Emperor only)

Grey Jedi/Neutral

 * Violet (Jedi/Grey Jedi): This indicates the lightsaber of a Jedi who stayed closely with their knowledge of the dark side as well as the light side. They walked a thin line between both of those paths. A combination of blue and red.
 * Dark violet: Stronger user of the force
 * Orange: Indicates the lightsaber of a Knight of Zakuul
 * Yellowish-Green (Grey Jedi): A blade with this color indicates a Jedi who tends to be very vain yet diverse in their training. A blade used typically by those who tread dangerously close to the dark side of the force as well as the light. (Taldav Only)

No Faction/Unknown

 * Silver: This lightsaber is what is called a dual-phase saber. Meaning the length of the blade can be changed with a special switch built into the hilt. The blade can be changed from the typical 1.2 meters to 2 meters with the flick of this switch.
 * Cyan: A lightsaber that holds this color generally emits a lower hum then others of different hue. Providing a bit of a bonus to stealth. The only downside is the loss in power energy drawn through the blade.
 * Clear: A clear beam improves the stealth of a character. This was generally used by Jedi who focused on stealth and reconnaissance missions. The only downside to this beam, is it made using the saber difficult during combat.
 * White: A color only used in lightsaber deflection training. This weapon provides no damage if someone is struck with it. Some sabers have been modified to create damage.
 * Magenta: No specific meaning
 * Brown: No specific meaning
 * Silver-Blue: No specific meaning
 * Rainbow (Shifts through the color spectrum): This lightsaber is unique in that it changes hue based upon the mood of the wielder. (Unavailable)