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