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