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