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