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