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