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