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