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