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