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