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