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