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