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