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