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