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