One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,4,6)(3,7,8,5)(9,10)(11,18)(12,27)(13,32)(14,21)(15,34)(16,22)(17,20)(19,23)(24,28)(25,30)(26,38)(29,36)(31,40)(33,39)(35,37)(9,10,17,32,15,21,33,24,16,22,28,39,14,34,13,20)(11,23,27,12,19,18,36,30,26,37,40,31,35,38,25,29)(1,3,4,8)(2,5,6,7)(9,11)(10,18)(12,20)(13,25)(14,35)(15,19)(16,26)(17,27)(21,37)(22,38)(23,34)(24,31)(28,40)(29,39)(30,32)(33,36)(9,12,28,38,15,30,13,23,16,31,17,18,14,29,33,37)(10,19,39,25,21,26,20,27,22,35,32,36,34,11,24,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.