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