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