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