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