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