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