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