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