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