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