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