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