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