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