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