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