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)(11,15)(12,16)(13,14)(17,20)(18,22)(19,21)(23,24)(25,26,30,32)(27,34,28,37)(29,35,31,39)(33,38,40,36)(3,7)(5,8)(10,14)(15,20)(16,21)(22,24)(26,32)(27,28)(35,39)(36,38) involution — undirected(1,3)(2,5)(4,7)(6,8)(9,11)(10,15)(12,18)(13,17)(14,20)(16,22)(19,23)(21,24)(25,27,30,28)(26,33,32,40)(29,36,31,38)(34,35,37,39)(2,6)(3,7)(11,17)(15,20)(18,23)(22,24)(25,28,30,27)(26,34,32,37)(29,36,31,38)(33,35,40,39)(9,12,13,19)(10,16,14,21)(11,18,17,23)(15,22,20,24)(25,29,30,31)(26,35,32,39)(27,36,28,38)(33,37,40,34)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.