When we designed the Mk.2 I ran dozens of test colour tints (which took a while, considering how long it takes to flush through an injection moulding machine) and decided on the colour you see now. It gives the best colour/brightness compromise since the VFD itself has quite a strong green component.

The first mini-batch of players actually shipped with a much deeper blue, which looked nice but was too dark to be useful in sunlight.

Rob