abstract: We study a stochastic boundary value problem on $(0,1)d$ of elliptic type in dimension $d\ge 4$, driven by a coloured noise. An approximation scheme based on a suitable discretization of the Laplacian on a lattice of $(0,1)d$ is presented; we also give the rate of convergence to the original SPDE in $Lp(\Omega;L{2}(D))$--norm, for some values of $p$.