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