Manipulate[With[{a = P[[1]], b = P[[2]]},
  p1 = Polygon[{{0, 0}, {0, a}, {a, a}, {a, 0}}];
  p2 = Polygon[{{0, a}, {0, a + b}, {a, a + b}, {a, a}}];
  p3 = Polygon[{{a, a}, {a, a + b}, {a + b, a + b}, {a + b, a}}];
  p4 = Polygon[{{a, 0}, {a, a}, {a + b, a}, {a + b, 0}}]];
 Show[Graphics[{RGBColor[1, 0, 0], {p1}}], 
  Graphics[{RGBColor[0, 1, 0], {p2, p4}}], 
  Graphics[{RGBColor[0, 0, 1], {p3}}], 
  Graphics[Text[x^2, {P[[1]]/2, P[[1]]/2}]], 
  Graphics[Text[y^2, {P[[1]] + P[[2]]/2, P[[1]] + P[[2]]/2}]], 
  Graphics[Text[xy, {P[[1]]/2, P[[1]] + P[[2]]/2}]], 
  Graphics[Text[xy, {P[[1]] + P[[2]]/2, P[[1]]/2}]], PlotRange -> All],
 Control[{{P, {1, 1}}, {0, 0}, {2, 2}, ImageSize -> {350, 200}}]]