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