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