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