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