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)(11,16)(12,15)(13,14)(17,18)(19,23)(20,24)(21,22)(25,26,29,32)(27,30,33,37)(28,35,36,31)(34,40,39,38)(2,4)(6,7)(9,11,14,12)(10,15,13,16)(18,21)(19,24)(27,33)(30,37)(34,39)(38,40)(17,19,22,24)(18,23,21,20)(25,26)(27,30)(28,31)(29,32)(33,37)(34,38)(35,36)(39,40)(1,3,5,8)(2,6,4,7)(9,12,14,11)(10,15,13,16)(17,20)(18,19)(21,24)(22,23)(25,27)(26,30)(28,34)(29,33)(31,38)(32,37)(35,40)(36,39)(1,4,5,2)(3,7,8,6)(9,13,14,10)(11,15,12,16)(17,21,22,18)(19,20,24,23)(25,28,29,36)(26,31,32,35)(27,34,33,39)(30,38,37,40)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.