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