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