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