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