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