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