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