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