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