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