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