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