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