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