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