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