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(9,13,26,38,15,29,14,30)(10,18,19,36,21,35,20,37)(11,22,12,27,24,39,23,28)(16,31,25,40,17,33,32,34)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.