Complex sentence: Anything between 2 and 32 colours (1 to 5 bitplanes) was supported, as well as a special 6th bitplane "extra half-brite" mode and the 6-bitplane Hold And Modify mode which allowed access to all 4096 colours at once.
Split into simpler sentences: Anything between 2 and 32 colours (1 to 5 bitplanes) was supported. A 6th bitplane was available for either the Halfbright mode that added a copy of the first 32 colours but with half the intensity or Hold And Modify mode which allowed access to all 4096 colours at once.