Will 12v led work for power led?

Solution
As Randomtech said, you are better off using a molex connector with 12V and attach it to a transistor to turn it on/off based on the voltage in the motherboard LED connector. You can even go one step further and use multiple 12V strips if you wanted to that way, and they would all turn on and off based on the computer's power state.
I suggest you take a course in electrical engineering (hell, even highschool circuits) before even trying to do anything like that. If you have to ask this question, you are going to make something catch fire or explode.

Proper way to do it is to first figure out what YOUR PSU uses, and then match the electrical characteristics (which will not be as simple as swapping out red for blue, since they have different voltages)
 
no, the LEDS wont work on the 5volts(well, if they did they would be extreamly dim.)
you would be better using a 12volt rail instead.

if you were going to do it the proper way, you would make up a little circuit with a transistor(power or mosfet one). with the signal from the motherboard(the frount panel power indicator(or similar)) to the base of the transistor and then the + side of the led strip going to 12volts, then the - side going into the collector and then hooking up the emitter (of the transistor) to the ground.
but that solution requires a bit of knowlege of electronics, and some soldering skills.
 
As Randomtech said, you are better off using a molex connector with 12V and attach it to a transistor to turn it on/off based on the voltage in the motherboard LED connector. You can even go one step further and use multiple 12V strips if you wanted to that way, and they would all turn on and off based on the computer's power state.
 
Solution
You really need some circuits lessons. It's not an insult, rather most of the questions would be very easy to answer with what you would learn in the first week of electrical engineering 101. At this rate you really will be causing severe damage to your equipment. I suggest you get yourself an arduino and prototype everything out. If it works, double check the math and apply it.
 
As suggested the easiest way is to connect to a Molex, you use black and yellow to give 12v output. This will be able to deliver more than enough current and will be powered as soon as the PC switches on. I have done this myself, currently have a set of LED strips which are supposed to be under car LED's for model cars, these have multiple patterns and colours I can adjust on a remote.

Pin layout http://www.bing.com/images/search?q=molex+pinout&view=detailv2&qpvt=molex+pinout&id=6F5407A455494A517647CE07ADF0FE76C3BF4A6D&selectedIndex=9&ccid=BY%2bBj9Pw&simid=608037717667286825&thid=OIP.M058f818fd3f0b5af2c4d25b338cd4e2ao0&ajaxhist=0

Also as said don't connect anything to the motherboard unless you get someone who really understands what they are doing.
 


One or possibly 2 will work, but any more will draw too much current, and damage your motherboard.