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