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