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)(12,22)(13,18)(14,19)(16,21)(17,23)(20,24)(25,26)(27,30)(28,31)(29,32)(33,35)(34,37)(36,38)(39,40) involution — undirected(1,3,4,8)(2,5,6,7)(9,11,14,21)(10,15,19,16)(12,23,20,13)(17,24,18,22)(25,27,29,35)(26,30,32,33)(28,34,36,40)(31,37,38,39)(9,12,23,11,14,20,13,21)(10,16,18,24,19,15,17,22)(25,26)(27,33,35,30)(28,31)(29,32)(34,39,40,37)(36,38)(2,6)(5,7)(25,28,29,36)(26,31,32,38)(27,34,35,40)(30,37,33,39)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.