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