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