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