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