The problem is that the lit element should be much brighter than the unlit elements and the hex grid. I think I'll wait until ciroip has a chance to dig out his vector images, or maybe he'll have another go at modding the tubes himself...

For reference, here's one of ciroip's original images:



and here's my modified version (of a different number, obviously):



I think making the glowing element any brighter will require adjusting other elements in the image, or maybe carefully tracing around the glowing element or something... quite a bit of work...