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)(11,15)(12,16)(13,14)(17,18)(19,23)(20,21)(22,24)(25,26,29,30)(27,33,34,31)(28,32,36,37)(35,39,40,38)(2,4)(6,7)(10,13)(15,16)(18,21)(19,24)(26,30)(27,34)(28,36)(38,39) involution — undirected(9,11,14,12)(10,15,13,16)(17,18)(19,22)(20,21)(23,24)(25,26)(27,31)(28,32)(29,30)(33,34)(35,38)(36,37)(39,40)(1,3)(2,6)(4,7)(5,8)(9,12,14,11)(10,16,13,15)(25,27,29,34)(26,31,30,33)(28,35,36,40)(32,38,37,39)(1,4,5,2)(3,7,8,6)(9,13,14,10)(11,16,12,15)(17,19)(18,22)(20,24)(21,23)(25,28,29,36)(26,32,30,37)(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.