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)(25,26,28,31)(27,35,37,40)(29,34,30,33)(32,36,39,38)(2,5)(6,8)(26,31)(27,36)(29,30)(32,35)(37,38)(39,40) involution — undirected(3,7)(6,8)(9,11,13,19)(10,14,16,23)(12,21,22,18)(15,24,20,17)(25,27,28,37)(26,32,31,39)(29,36,30,38)(33,40,34,35)(1,3,4,7)(2,6,5,8)(27,37)(32,39)(35,40)(36,38)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.