These give an nice 216 colour cross selection of all colours, that will still fit in the RAMDAC of an 8 bit (256 colour) video card, leaving 40 colours over for the system.
This page is drawn as 6 blocks with increasing amounts of red, each showing all 6x6 green/blue combinations with that amount of red. It is in 6x1 blocks arrangement, it is also available in 3x2 blocks arrangment.
This page is by Neil Franklin, last modification 2000.12.30