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