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