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