I am not sure if this is the right section but it should be related to the motherboard.
I recently put a new power supply in the computer. Everything is hooked up right because it booted up with no problems, no beeps, no sounds. Games run good, everything is smooth.
However, there is a red light on the front panel. It's not on all the time. But for example if I open 10 Firefox windows in a row right now it will start flickering red. Sometimes it just flickers red when I am doing nothing. Or if I am just doing some typing like this.
Before I replaced the PSU it was usually a green light which is noticeable. I haven't seen the green go on yet.
In the absence of any symptoms I would think you have nothing to worry about. Check the cabling that goes from the front panel to the motherboard and make sure that is all wired correctly. If you like you can disconnect the front panel HDD cable which goes from the front panel to the motherboard. If the red light goes away then you know for sure what it is but it sounds like a HDD indicator to me. As for the green light make sure the other front panel cables are in place and seated correctly. It may be a power indicator which has come off the board while you were installing the PSU.
If the PC is running fine you have nothing to worry about. Maybe the case had a green led light that has failed. Or maybe there is a cooling fan that put out a green light that you haven't plugged in. Or maybe the light on a cooling fan has failed thus no more green light. I wouldn't worry about it but check all your cooling fans.