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