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