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