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