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)(11,19)(12,21)(13,16)(14,20)(15,17)(18,23)(22,24)(1,3,5,8)(2,6,7,4)(9,11,15,13)(10,16,17,19)(12,22,23,20)(14,18,24,21)(25,26)(27,32)(28,33)(29,34)(30,31)(35,39)(36,40)(37,38)(1,3)(2,4)(5,8)(6,7)(10,17)(12,23)(16,19)(20,22)(26,31)(27,35)(33,37)(34,36) involution — undirected(1,4)(2,3)(5,6)(7,8)(9,12)(10,18)(11,20)(13,22)(14,16)(15,23)(17,21)(19,24)(25,27,30,35)(26,32,31,39)(28,36,38,34)(29,33,40,37)(9,13,15,11)(10,19,17,16)(12,22,23,20)(14,18,24,21)(25,28)(26,33)(27,36)(29,39)(30,38)(31,37)(32,40)(34,35)(9,14,15,24)(10,20,17,22)(11,18,13,21)(12,19,23,16)(25,29,30,40)(26,34,31,36)(27,37,35,33)(28,32,38,39)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.