you need 3 leds (with resistor attatched), i bought a set of leds from ebay
(T5/BS.30 LED INSTRUMENT CLUSTER & GAUGE ILLUMINATION BULB),
They didnt quite go in as direct replacements, but i soldered 2 legs onto each led & just soldered them onto the membrane of the clocks.
you can just snap out (carefully) the old bulbs, solder in the new ones onto the existing contacts (watch the polarity though +/- )
, ive re-done all the interior lights in my mkII to blue
