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