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