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