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