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