\documentclass[12pt]{article} \usepackage{amssymb,amsmath,amscd,concmath,amsfonts} \usepackage{color} \pagestyle{empty} \begin{document} \begin{equation*} \aligned u &= u_e - K(x - x_e) + k_r ({\color{blue} L_d} - y_e) \\ &= {\color{blue} -} \begin{bmatrix} 0.025 & -0.052 \end{bmatrix} \begin{bmatrix} H - 20.6 \\ L - 29.5 \end{bmatrix} + 0.002\, ({\color{blue} L_d} - 29.5). \endaligned \end{equation*} \end{document}