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