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