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