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