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