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