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