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