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