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