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