I'm using this amp with Sony xplode 12" and i'm wondering why the amp turns from green to red after a long time of listening so my sub dont work. does it look like i need a capacitor?

 

check your manual, for both amp and sub, look at what the colors mean on the amp... then since i bet it is overheating since it happens after a while.... check the wiring and make sure the Ohm load isnt too great.. Also, make sure if heat is the code... that the amp has pleanty of ventilation, and if it has fins as the heatsink make sure the fins are in a way in which they would be up and down like this ||||||||| since heat rises... said same thing in my manual, for kenwood, whether or not it makes a huge difference I bet depends on the size of the sinks and such...

EDIT: dont jump for Caps so soon (very expensive, and not too much use in non serious system creators), they are only needed to even out very short spikes in the current, their max charge only lasts a few seconds if that... if too little power is the problem, get your system tested, maybe get a new better battery, or alternator... But I really doubt that is the problem here.