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