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