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