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