Quite simple really! Remove the front panel and snip off the red and black wires close to the red LED. Now turn the front panel face down as shown and press downward..... this should release the red LED from the hole on the front panel:

LED assembly (ready to fit) can be ordered from me. Please contact me to check price / availability.

Now you solder a 5mm blue (diffused) LED (L-53MBD) onto the black and red wires........ be sure to connect the long lead of the LED to the red wire and the short lead of the LED to the black wire. You will have to solder a resistor in series with the red lead / long lead of the LED and a good value to use is 5K this will give you a nice subdued blue glow.... you can omit the 5K resistor if you want but the blue LED will glow very bright.

Be sure to insulate one or both of the leads with heatshrink

Once you have soldered the new LED (and series resistor) onto the black and red leads simply pop it into the hole and secure with a small blob of hot glue (or superglue) Voila! Job done!