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