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