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)(11,14)(12,16)(13,15)(19,23)(21,24)(26,30)(27,33)(28,35)(38,40) involution — undirected(1,3,5,8)(2,6,7,4)(9,11,15,16)(10,12,13,14)(17,18,20,22)(19,21,23,24)(26,30)(27,33)(32,37)(34,39)(2,7)(3,8)(9,12,15,14)(10,16,13,11)(25,26,29,30)(27,31,33,36)(28,32,35,37)(34,38,39,40)(1,2)(3,6)(4,8)(5,7)(9,13,15,10)(11,12,16,14)(17,19)(18,21)(20,23)(22,24)(25,27)(26,31)(28,34)(29,33)(30,36)(32,38)(35,39)(37,40)(1,4,5,6)(2,8,7,3)(9,14,15,12)(10,16,13,11)(25,28)(26,32)(27,34)(29,35)(30,37)(31,38)(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.