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