There are various gem sockets available on gear that allows a degree of personalisation of stats and also the ability to gain bonus stats through socket bonuses where the gem color and gem socket color match.
This however does not always provide the best stats available dependng on what the bonus is in relation to what role or situation the player finds themselves in, an example of this would be stacking resilience and stamina in red sockets for a tank in PvP.
There are three colored socket types: red, yellow, and blue. Any gem can be placed into any socket, and you will receive the bonus for that gem.
If all the gems match all the sockets they have been placed in on an item an additional socket bonus will be awarded.
Uncolored sockets are generally sockets that have been added to an item by blacksmithing skills (or blacksmithed items). Any gem (except meta gems) may be placed in them.
The exception to this is relics either made by Inscription,looted from dungeon inhabitents or purchased with or
Uncolored sockets and the gems that have been added to items via blacksmithing do not count towards any socket bonus an item may have.
Sockets in Relics do count as the sockets are an integral part of the item and are usually the only socket on the item in question.
In both of these situations the gems color will count towards any requirements of a meta gem.
Meta gem's differ from colored gems as they also have a requirement for them to activate,
Meta gems require a certain combination of other color gems currently socketed in your equipped gear for both the meta gem and the socket bonus on the gear to be activated
(Note: Meta sockets are only found on high-end head gear.)
A stat is associated with a primary color (red, yellow, blue). For example, strength is a red stat. That means having a pure strength gem in a yellow or blue slot is possible but the gem color bonus requirement will not be met.
However, gems come in both primary and secondary colors. As seen on the Color Wheel below, if you mix red and yellow, you get orange. An orange gem will provide one red stat and one yellow stat, each in approximately one-half the amount that a primary-colored gem of the same level would.
It is most important to note that, for the purposes of both socket bonuses and meta-gem requirements, a secondary-colored gem is considered to be a gem of BOTH of its primary colors. Thus, an orange gem will be considered to be both a red gem AND a yellow gem at the same time.
Therfore if a gem requires more red than yellow gems equipping an orange gem will not affect the balance
This means that if you really want strength, and your item only contains a yellow socket, then the only way to get both strength and the socket bonus is with an orange gem, which will reduce the strength stat and suppliment it with a yellow stat like critical strike rating or resilience.
This table shows all existing stat mixes and their name prefixes.