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