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