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