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)(11,15)(12,17)(13,21)(14,18)(16,19)(20,24)(22,23)(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)(10,15)(12,19)(13,22)(14,20)(16,17)(18,24)(21,23)(26,31)(27,36)(29,30)(32,35)(37,38)(39,40)(9,11)(10,16)(12,19)(13,22)(14,20)(15,21)(17,24)(18,23)(25,27,28,37)(26,32,31,39)(29,36,30,38)(33,40,34,35)(2,6)(5,7)(9,12,14,13)(10,17,18,21)(11,19,20,22)(15,16,24,23)(26,31)(27,37)(33,34)(36,38)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.