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