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