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