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