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