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)(25,26,32,35,31,29,30,36)(27,28,38,33,37,40,34,39)(1,3,4,7)(2,5,6,8)(11,18)(12,21)(14,17)(15,20)(25,27)(26,33)(28,35)(29,39)(30,38)(31,37)(32,34)(36,40)(2,6)(5,8)(9,11)(10,14)(12,19)(13,18)(15,22)(16,17)(20,23)(21,24)(25,28,31,40)(26,34,29,38)(27,36,37,35)(30,39,32,33)(11,18)(14,17)(19,24)(22,23)(25,29,32,36,31,26,30,35)(27,28,38,33,37,40,34,39)(9,12,13,21)(10,15,16,20)(11,19,18,24)(14,22,17,23)(25,30,31,32)(26,35,29,36)(27,34,37,38)(28,33,40,39)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.