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