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