Given two vector plots and a contour plot like the following
as = VectorPlot[{Cos[y], Sin[x] }, {x, -3, 3}, {y, -3, 3},
VectorScale -> Automatic, VectorColorFunction -> "Rainbow"
];
bs = StreamPlot[{Cos[y], Sin[x] }, {x, -3, 3}, {y, -3, 3},
VectorScale -> Automatic, StreamColorFunction -> "Rainbow"
];
cs = ContourPlot[Cos[x] + Sin[y], {x, -3, 3}, {y, -3, 3},
ColorFunction -> "BlueGreenYellow"
];
Show[cs, bs, as]

we can see basic superimposing job is well done by Show[]. But my question is how can I control the opacity of the background contour plot cs? Also, how can I insert “BlueGreenYellow” type color schemes in a color function like the following?
ContourPlot[Cos[x] + Sin[y], {x, -3, 3}, {y, -3, 3},
ColorFunction -> (Directive[Opacity[#],Blue] &)
];
You can try using
BaseStyleas follows: