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