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