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