{g1, g2, b} = {x + 2 y, 2 x + y, {2, 2}};

    coloresRest = {Blue, Magenta};

    labels = MapIndexed[Framed[Style["(" <> ToString@#2[[1]] <> ")", #, 18], 
         FrameStyle -> None, Background -> White] &, coloresRest];

    Show[MapThread[
          ContourPlot[#, {x, -2, 4}, {y, -2, 4}, 
             Frame -> False, 
             Axes -> True,
             ContourShading -> None, 
             Contours -> {0}, 
             ContourStyle -> Directive[#2, Thick], 
             ContourLabels -> Function[{x, y, z}, Text[#3, {x, y}]], 
             ImageSize -> 400] &, 
          {{g1 - b[[1]], g2 - b[[2]]}, coloresRest, labels}]] 

[![enter image description here][1]][1]


  [1]: https://i.sstatic.net/ZXqiL.png