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