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