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