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