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)(11,19)(12,16,24,31)(13,17)(14,27)(15,21)(18,26)(20,28,36,33)(22,29)(23,37,38,30)(25,40,39,32)(34,35)(2,6)(7,8)(9,11)(10,15)(12,23,24,38)(13,21)(14,22)(16,30,31,37)(17,19)(18,29)(20,25,36,39)(26,35)(27,34)(28,32,33,40)(1,3,5,4)(2,7,6,8)(9,12,14,25,13,24,26,39)(10,16,27,40,17,31,18,32)(11,20,35,38,21,36,22,23)(15,28,29,30,19,33,34,37)(1,4,5,3)(2,7,6,8)(10,17)(15,19)(16,31)(18,27)(28,33)(29,34)(30,37)(32,40)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.