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