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