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