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