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