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