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)(11,19)(12,16)(13,17)(14,18)(15,21)(20,24)(22,23)(25,26,31,33,30,32,28,38)(27,35,37,39,36,29,34,40)(9,11,14,21)(10,15,18,19)(12,20,13,22)(16,23,17,24)(25,27,30,36)(26,29,32,35)(28,34,31,37)(33,40,38,39)(1,3,5,4)(2,6,7,8)(9,12,14,13)(10,16,18,17)(11,20,21,22)(15,23,19,24)(26,32)(27,36)(33,38)(34,37)(9,13,14,12)(10,17,18,16)(11,20,21,22)(15,23,19,24)(25,28,30,31)(26,33,32,38)(27,37,36,34)(29,39,35,40)(1,4,5,3)(2,6,7,8)(10,18)(15,19)(16,17)(23,24)(25,29,28,39,30,35,31,40)(26,34,38,36,32,37,33,27)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.