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