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