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