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