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