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