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