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