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