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