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)(27,32)(28,31)(29,34)(30,33)(35,38)(36,39)(37,40) 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)(25,27,31,34)(26,32,28,29)(30,35,39,40)(33,38,36,37)(10,16)(15,17)(18,23)(22,24)(26,28)(27,34)(33,36)(35,40) 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)(25,28,31,26)(27,29,34,32)(30,36,39,33)(35,37,40,38)(1,4,5,3)(2,8,6,7)(9,12,14,11)(10,17,16,15)(13,20,21,19)(18,24,23,22)(25,29)(26,27)(28,34)(30,38)(31,32)(33,40)(35,36)(37,39)(9,13,14,21)(10,18,16,23)(11,19,12,20)(15,22,17,24)(25,30)(26,33)(27,35)(28,36)(29,37)(31,39)(32,38)(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.