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