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