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