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