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)(11,17,21,24)(12,22,20,15)(13,23,19,18)(25,26,28,31)(27,33,35,30)(29,32,36,39)(34,40,37,38)(1,3,4,8)(2,5,6,7)(9,11,19,12,14,21,13,20)(10,15,23,24,16,22,18,17)(27,34)(29,36)(30,38)(32,39)(33,40)(35,37)(2,6)(5,7)(10,16)(15,22)(17,24)(18,23)(25,27,28,35)(26,30,31,33)(29,37,36,34)(32,40,39,38)(2,6)(5,7)(9,12,19,21,14,20,13,11)(10,17,23,15,16,24,18,22)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.