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