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