Thinking of NEXTSTEP this morning...I'd guess many aren't aware of the unusual color display arrangement.
The NeXTstation, which was the first "affordable" color solution for NEXTSTEP, has a 16-bit framebuffer, but instead of rendering the desktop in 65,536 colors (as per Windows or Mac hardware, say), it rendered in 12-bit color with 4-bits of alpha channel (transparency).
That means it had a palette of 4096 colors, with all colors available at once on the display (not like, say, the Amiga or Apple IIgs with a 4096 color palette, but video modes with a small subset of those colors available (yes, yes, HAM mode excluded). Additionally, anything on the screen had 16 levels of opacity available.
It's interesting to see in person, on the actual hardware (especially on a good LCD display). With dithering, it looks very close to 24-bit truecolor.
(The NeXT Dimension color board for the Cube allowed 24-bit color with 8-bits alpha, but that was not so frequently used -- less so than most NeXT hardware even...)
But that's not nearly the weirdest that NEXTSTEP-capable hardware got, when it came to color video display...
Some workarounds for missing 
