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