Friendly reminder from a neighborhood jewelcrafter
You do not need to socket the "right" color for gems in socketed gear.
If a socket color is yellow, you do not need to socket a yellow gem. Inspect the "Socket Bonus". If this is not useful for you (they aren't always - sometimes there is a +resilience bonus which only matters for pvp, or sometimes a +stamina bonus on a character that doesn't really need stam) you may choose not to socket the right colors. By ignoring the socket bonus sometimes you can come up with an item that has a highly superior combination of stats than if you did follow the socket bonus.
One example is the mage's spellfire set. You could either socket for colors and get a socket bonus of a very "exciting" 3 stamina... or you could socket with +9 damage gems and get additional damage. On my mage, I chose to socket all of my Spellfire gear with pure +dmg. Naturally this leaves my stamina pretty low... so I also carry a separate stamina set with me when I know I will need one. Trying to make Spellfire into something it is not (a high stamina set) is much more difficult than simply carrying two different items. That way spellfire can remain what it is supposed to be (the best armor for a fire mage until tier 5/6) and you can have separate items to care care of your stamina needs. In an instance, if you behave, you should rarely be hit, and the stamina bonus will not help you very much unless you ARE hit :)
Also note that a "Yellow" gem slot does not need to be satisfied by a yellow gem. There are some gems that count as two colors. "Orange" counts as yellow and red. "Green" counts as yellow and blue. This also works toward meta gems which I will discuss next.
Meta gem requirements can be satisfied by "mixed color" gems
Take the Insightful Earthstorm Diamond. It requires 2 red, 2 yellow, and 2 blue gems. If you have 2 green gems and 2 red gems in your gear, that DOES satisfy the requirement. 2 red gems = 2 red. EACH green gem counts as 1 blue and 1 yellow. It counts for both colors.
Don't let meta gems OR socket colors rule your gear.
I had a healing meta gem that required that I always have more red gems than blue gems AND more yellow gems than blue gems. I found myself socketing gear the way I didn't want to socket it because of this requirement. It was not fun - I couldn't socket Purple gems without socketing more Orange gems, and Orange gems aren't particularly great for a healing druid - int and +healing, but I wanted more regen instead of intellect, and for that I needed to socket a purple gem (+healing and mp5/spirit).
Since I dropped that Meta and went with Insightful Earthstorm Diamond, I have been a much happier druid.
Meta gems are expensive - just make sure you look at them and think about how practical it is for you to use and keep up with the requirements before you buy one :)
The same goes for regular sockets. As I said above, if you don't want a socket bonus, you don't have to take it. Gems are flexible and can fill in slots where you need to fill in. On PvP gear, if you need more stamina or resilience, you can socket for it. Unless you are simply dying for that socket bonus, pay attention to what the bonus is before you socket for it. If you don't want to socket for the bonus, and can't find a blue gem you want to socket, that's fine!
If a socket color is yellow, you do not need to socket a yellow gem. Inspect the "Socket Bonus". If this is not useful for you (they aren't always - sometimes there is a +resilience bonus which only matters for pvp, or sometimes a +stamina bonus on a character that doesn't really need stam) you may choose not to socket the right colors. By ignoring the socket bonus sometimes you can come up with an item that has a highly superior combination of stats than if you did follow the socket bonus.
One example is the mage's spellfire set. You could either socket for colors and get a socket bonus of a very "exciting" 3 stamina... or you could socket with +9 damage gems and get additional damage. On my mage, I chose to socket all of my Spellfire gear with pure +dmg. Naturally this leaves my stamina pretty low... so I also carry a separate stamina set with me when I know I will need one. Trying to make Spellfire into something it is not (a high stamina set) is much more difficult than simply carrying two different items. That way spellfire can remain what it is supposed to be (the best armor for a fire mage until tier 5/6) and you can have separate items to care care of your stamina needs. In an instance, if you behave, you should rarely be hit, and the stamina bonus will not help you very much unless you ARE hit :)
Also note that a "Yellow" gem slot does not need to be satisfied by a yellow gem. There are some gems that count as two colors. "Orange" counts as yellow and red. "Green" counts as yellow and blue. This also works toward meta gems which I will discuss next.
Meta gem requirements can be satisfied by "mixed color" gems
Take the Insightful Earthstorm Diamond. It requires 2 red, 2 yellow, and 2 blue gems. If you have 2 green gems and 2 red gems in your gear, that DOES satisfy the requirement. 2 red gems = 2 red. EACH green gem counts as 1 blue and 1 yellow. It counts for both colors.
Don't let meta gems OR socket colors rule your gear.
I had a healing meta gem that required that I always have more red gems than blue gems AND more yellow gems than blue gems. I found myself socketing gear the way I didn't want to socket it because of this requirement. It was not fun - I couldn't socket Purple gems without socketing more Orange gems, and Orange gems aren't particularly great for a healing druid - int and +healing, but I wanted more regen instead of intellect, and for that I needed to socket a purple gem (+healing and mp5/spirit).
Since I dropped that Meta and went with Insightful Earthstorm Diamond, I have been a much happier druid.
Meta gems are expensive - just make sure you look at them and think about how practical it is for you to use and keep up with the requirements before you buy one :)
The same goes for regular sockets. As I said above, if you don't want a socket bonus, you don't have to take it. Gems are flexible and can fill in slots where you need to fill in. On PvP gear, if you need more stamina or resilience, you can socket for it. Unless you are simply dying for that socket bonus, pay attention to what the bonus is before you socket for it. If you don't want to socket for the bonus, and can't find a blue gem you want to socket, that's fine!