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