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