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