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