[Tex/LaTex] Change color of QED symbol

amsmathcolor

I wanted to know how to change the color of the QED symbol. Here is my code where I would like the QED symbol color to be changed to my defined color:

\documentclass{book}
\usepackage{amsmath,amsfonts,amssymb,amsthm}
\usepackage{xcolor}
\definecolor{ocre}{RGB}{52,177,201}

\begin{document}

\begin{align}
  \boldsymbol{\theta}=&\mathbf{H}^{-1}(k)\mathbf{Z}(k)\\
  \Rightarrow {\begin{pmatrix}
  x(0) \\ \dot{x}(0)
\end{pmatrix}}
=&{\begin{pmatrix}
  x_{1} & x_{2} \\ x_{3} & x_{4}
\end{pmatrix}}^{-1}
{\begin{pmatrix}
  x(t_{1}) \\ x(t_{2})
\end{pmatrix}}
\end{align}
\qed
\end{document}

Best Answer

The standard definition of \qedsymbol is \openbox. Just do

\renewcommand{\qedsymbol}{\textcolor{ocre}{\openbox}}

Full code (note the loading of bm that's recommended for \boldsymbol, that can also be shortened into \bm):

\documentclass{book}
\usepackage{amsmath,amssymb,amsthm,bm}
\usepackage{xcolor}
\definecolor{ocre}{RGB}{52,177,201}
\renewcommand{\qedsymbol}{\textcolor{ocre}{\openbox}}

\begin{document}

\begin{align}
  \boldsymbol{\theta}=&\mathbf{H}^{-1}(k)\mathbf{Z}(k)\\
  \Rightarrow {\begin{pmatrix}
  x(0) \\ \dot{x}(0)
\end{pmatrix}}
=&{\begin{pmatrix}
  x_{1} & x_{2} \\ x_{3} & x_{4}
\end{pmatrix}}^{-1}
{\begin{pmatrix}
  x(t_{1}) \\ x(t_{2})
\end{pmatrix}}
\end{align}
\qed
\end{document}

enter image description here

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