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