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