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