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