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