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