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