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