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