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