Multiple Voltage (230VAC & 110VAC) panel indication
You can use a neon indicator as @Brian suggests or use a 240VAC LED indicator (since neons eventually fail 'off'). 

The apparent difference in brightness is not actually that great because of the logarithmic response of the human eye. The LED will be even less sensitive since it doesn't have much voltage drop compared to the neon. I would suggest buying a couple and actually trying it before rejecting the simplest solution. 

If the difference really bugs you, you could use a capacitor dropper with series resistance and clamp the voltage with a zener (a resistive dropper will likely have excessive dissipation if you clamp it with 240VAC applied), but all that stuff is at mains voltage and it has to be dealt with in a safe manner- vs. just buying an approved LED or neon lamp assembly. 



Edit: Here is an example LED panel indicator (similar to neon types in size- fits a ~8mm hole) that is rated 125 to 250VAC: (Bulgin P/N LE2950WL5A)