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