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