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