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