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