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