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