T. Ment wrote:

My computer case green led failed. I bought some on Ebay, but they are
so bright they light up the room and obscure the other color leds.

Any suggestions for a cheap source of low intensity leds in a 3mm size?
Maybe Mouser, but then $1 worth of parts costs $10 to ship. If I have to
spend that much to fix it, I'll just live without a power led.

Can you add a resistor or something to change the brightness?

You could go through what Paul mentions. Just remember to get some
heatshrink tubing to slide onto the wire, solder the resistor to the
cable wire, slide up the tubing, and heat to coat the bare wires.

Another possibly is scotch tape which is a bit frosted. I don't know
the LED you have fit into the holder in the case. You might be able to
layer a dozen pieces of scotch tape, trim it off using an exacto blade
to match the diameter of the LED's face, and check it still snaps into
the case holder. Else, you could buy some self-stick rubber feet that
are translucent and stick them over the LED opening in the case. The
idea is to attenuate the output via diffusion rather than via voltage
change.