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