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