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