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