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