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