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