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