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