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