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