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