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