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