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