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