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