From what I understand, while the display itself supports more than 4 shades, Hijack's sreenbuf is just 2048 bytes, so > 4 shades can't be represented. I think the stuff Toby does in the visuals involves straight assembly to the display which allows more "shades."
I don't remember seeing any kernel mechanism that would allow him to do so - 3 shades + black appears to be it.
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Mk2a 60GB Blue. Serial 030102962 sig.mp3: File Format not Valid.