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