If you mean the red LEDs in the fan(s), yes. just cut the leads to the LEDs. You'll want to make sure the cut leads can't wander by tacking the cut ends down with some glue or clear tape. Though if it is possible you may sell the case in the future, then your buyer may want the LEDs. So it might be a better idea just to replace the LED fans with some better, plain black ones and store the LED fans away for that time.
.bh.