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