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