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