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)(11,17)(12,14)(13,16)(15,18)(19,24)(20,22)(21,23)(26,30)(31,33)(32,36)(38,39)(1,3,5,8)(2,6,7,4)(10,12)(11,18)(16,20)(19,21)(25,26)(27,33)(28,32)(29,30)(31,34)(35,39)(36,37)(38,40)(1,3)(2,4)(5,8)(6,7)(10,12)(15,17)(16,20)(23,24)(27,34)(31,33)(35,40)(38,39) involution — undirected(1,4)(2,3)(5,6)(7,8)(9,11)(10,15)(12,17)(13,21)(14,18)(16,24)(19,22)(20,23)(25,26)(27,31)(28,36)(29,30)(32,37)(33,34)(35,39)(38,40) involution — undirected(9,12,14,10)(11,17,18,15)(13,20,22,16)(19,24,21,23)(25,27,29,34)(26,31,30,33)(28,35,37,40)(32,38,36,39)(9,13,14,22)(10,16,12,20)(11,19,18,21)(15,23,17,24)(25,28)(26,32)(27,35)(29,37)(30,36)(31,38)(33,39)(34,40)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.