according to the manual there are multiple led's. is it the cpu led or the ram? also you said its red in the title but then you say its green. check the ram and try the a single stick and then in a different slot.
The POST State LEDs of CPU, DRAM, VGA card, and HDD indicate key components status during POST (Power-on Self Test). If an error is found, the LED next to the error device will continue lighting until the problem is solved. This user-friendly design provides an intuitional way to locate the root problem within a second.