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