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