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