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