I'm just using coloured LEDs - they didn't have any white ones in the shop when I bought them. Would like to try out some of Tims filtering ideas in the neat future though. I reckon that is the was to go - then you are really flexible.
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(list 6284, Mk1 S/N 00299 4GB blue [sold]. Mk2 S/N 080000094 20GB blue)