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