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