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