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