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