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