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