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