The original NeXTcube was 4-bit grayscale, but there was a graphics card available which supported 24-bit colour. The later NeXTstations supported 12-bit colours without any additional hardware.

> was 4-bit grayscale

Small nitpick: it was 2-bit and could do two greys in addition to black and white.

Thank you. I actually knew that; I was thinking “4 shades”, and then wrote “4-bit” by mistake.