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