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