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