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