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