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