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)(32,38)(35,37)(39,40)(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)(28,35,38,32,37,36,39,40)(1,3,5,4)(2,7,8,6)(10,15)(11,17)(16,22)(18,23)(25,28,30,39,31,37,29,38)(26,32,27,35,34,40,33,36)(1,4,5,3)(2,6,8,7)(12,19)(16,22)(18,23)(20,24)(28,37)(32,40)(35,36)(38,39)(9,12,13,19)(10,16,15,22)(11,18,17,23)(14,20,21,24)(25,29,31,30)(26,27,34,33)(28,38,37,39)(32,35,40,36)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.