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