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