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