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