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