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