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