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