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