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