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