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