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