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