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