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