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