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