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