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)(15,20)(16,21)(22,24)(25,26)(27,33)(28,31)(29,37)(30,32)(34,38)(35,39)(36,40) involution — undirected(2,5)(6,7)(9,10,13,14)(11,15,18,20)(12,16,19,21)(17,22,23,24)(25,27,30,28)(26,31,32,33)(29,35,38,36)(34,39,37,40)(1,2)(3,6)(4,5)(7,8)(12,19)(16,21)(17,23)(22,24)(26,32)(31,33)(34,37)(39,40) involution — undirected(1,3)(2,6)(4,8)(5,7)(9,10)(11,15)(12,16)(13,14)(17,22)(18,20)(19,21)(23,24)(25,28,30,27)(26,33,32,31)(29,36,38,35)(34,40,37,39)(9,11,13,18)(10,15,14,20)(12,17,19,23)(16,22,21,24)(25,29)(26,34)(27,35)(28,36)(30,38)(31,39)(32,37)(33,40)(9,12,13,19)(10,16,14,21)(11,17,18,23)(15,22,20,24)(25,26)(27,31)(28,33)(29,34)(30,32)(35,39)(36,40)(37,38)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.