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