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