Grid[
MapThread[PlusMinus, {m1, m2}, 2],
BaseStyle -> 15,
ItemStyle -> {{Red, Blue}, {}, {1, 1} -> {18, Bold}}]
DisplayForm@RowBox[{"(", #, ")"}] & [%]
###Edit
m1 = Map[Style[#, 18, Bold] &, {{a1, a2}, {b1, b2}}, {2}];
m2 = {{u1, v1}, {u2, v2}};
Grid@MapThread[PlusMinus, {m1, m2}, 2]
