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