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