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