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