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