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