One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,4)(9,10)(11,21,24,16)(12,26,28,34)(13,19)(14,20)(15,18)(17,27,33,29)(22,36)(23,32,25,31)(30,37)(35,38)(39,40)(5,6)(7,8)(9,11,14,25,15,24,13,23)(10,16,20,32,18,21,19,31)(12,22,29,38,28,39,27,37)(17,30,34,36,33,35,26,40)(2,4)(6,8)(9,12)(10,17,18,33)(11,22)(13,27)(14,29)(15,28)(16,30,21,35)(19,26,20,34)(23,37)(24,39)(25,38)(31,40,32,36)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.