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