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