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