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