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)(11,19)(12,23)(13,24)(14,18)(15,22)(16,21)(17,20)(26,30)(27,33)(32,37)(34,39) involution — undirected(1,2,4,6)(3,5,8,7)(9,11)(10,15)(12,20)(13,21)(14,22)(16,17)(18,19)(23,24)(25,26,29,30)(27,31,33,36)(28,32,35,37)(34,38,39,40)(1,2)(3,5)(4,6)(7,8)(25,26)(27,31)(28,32)(29,30)(33,36)(34,38)(35,37)(39,40) involution — undirected(1,3,4,8)(2,5,6,7)(9,12,14,21)(10,16,18,23)(11,20,22,13)(15,17,19,24)(25,26)(27,31)(28,32)(29,30)(33,36)(34,38)(35,37)(39,40)(9,13,14,20)(10,17,18,24)(11,21,22,12)(15,16,19,23)(25,27,29,33)(26,31,30,36)(28,34,35,39)(32,38,37,40)(9,10)(11,15)(12,23)(13,17)(14,18)(16,21)(19,22)(20,24)(25,28,29,35)(26,32,30,37)(27,34,33,39)(31,38,36,40)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.