\documentclass[12pt]{article}
\usepackage{amssymb,amsmath,amscd,concmath,amsfonts}
\usepackage{color}
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\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}