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