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