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