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