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