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