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