A while back, I described how to put lights on the dash in this thread:-
http://igmaynard.co.uk/bongo/forum/view ... 44&t=64651
I've now found a much better alternative to using the original bulbs.
You still need the bulb holder but run a 3mm drill through it, which is easy enough to do, then stick a 3mm LED into the hole (Maplin do them in various colours - avoid the bright ones).
It still pays to put a bit of coloured plastic in front of the LED to disperse the light and make it less white
For comparison, here's a photo of the dash light for the rear fog light:-
And here's a green LED light, which indicates power to the glowplug rail:-
In the photos, the LED doesn't look quite as good but, in practice, there's little difference although the bulb still has the edge.