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