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