How to change the style of the cross reference in cleveref package?

Question

I want to change the style of the crossed reference (chapter, section, figure, equation, ...) generated by using cleveref package, for example, put parentheses around the referenced item and use boldface for the numbers.

\documentclass[14pt,a4paper]{extreport}
\usepackage[left=2.00cm, right=1.50cm]{geometry}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{graphicx}
\usepackage{xcolor}
\usepackage{lipsum}
\usepackage{hyperref}  
\hypersetup{colorlinks=true,citecolor=red, linkcolor=blue}
\usepackage{cleveref}
\usepackage{tcolorbox}
\begin{document}
\chapter{First  Chapter}\label{ch:chapter 1}
\section{Section One}\label{sec:section one}
\lipsum[1]
\section{Section Two}\label{sec:section two}
\begin{align}
r =& \sqrt{x^2 + y^2}\label{eq:equation 1}\\[2ex]
z =& \sqrt[3]{1 - 2r^2}\label{eq:equation 2}
\end{align}
see \cref{sec:section one} in \cref{ch:chapter 1}\\
\Cref{eq:equation 1} is the governing equations, \cref{eq:equation 2} is the second equation.
\end{document}

Answer 1

If the numbers and the surrounding parentheses should be typeset in bold, add the instructions

\crefdefaultlabelformat{#2\bfseries\upshape(#1)#3}          
\creflabelformat{equation}{#2\bfseries\upshape(#1)#3}

after loading cleveref.

If only the numbers but not the surrounding parentheses should be typeset in bold, issue the instructions

\crefdefaultlabelformat{#2(\textbf{\textup{#1}})#3}
\creflabelformat{equation}{#2(\textbf{\textup{#1}})#3}

Observe the use of \upshape/\textup to make sure that the number (and, if required, the parentheses) are always typeset in the upright font shape.

A full MWE (minimum working example) that renders both the numbers and the surrounding parentheses in bold:

\documentclass[14pt,a4paper]{extreport}
\usepackage[left=2cm, right=1.5cm]{geometry}
\usepackage[utf8]{inputenc}
\usepackage{amsmath,amsfonts,amssymb,graphicx,xcolor}

\usepackage{hyperref}  
\hypersetup{colorlinks=true,linkcolor=blue}

\usepackage{cleveref}
\crefdefaultlabelformat{#2\bfseries\upshape(#1)#3}
\creflabelformat{equation}{#2\bfseries\upshape(#1)#3}

\usepackage{tcolorbox}

\begin{document}
\chapter{First  Chapter}\label{ch:chapter 1}
\section{Section One}\label{sec:section one}
\section{Section Two}\label{sec:section two}
\begin{align}
r =& \sqrt{x^2 + y^2}\label{eq:equation 1}\\[2ex]
z =& \sqrt[3]{1 - 2r^2}\label{eq:equation 2}
\end{align}

See \cref{sec:section one} in \cref{ch:chapter 1}.

\Cref{eq:equation 1} is the governing equation, and  \cref{eq:equation 2} is the second equation.
\end{document}

---

Addendum to address the OP's follow-up comment: Use the instructions

\crefdefaultlabelformat{(#2\textbf{\textup{#1}}#3)}
\creflabelformat{equation}{(#2\textbf{\textup{#1}}#3)}

if only the cross-referenced numbers, but not the surrounding parentheses, should be rendered in bold and be made into hyperlink targets (and hence be rendered in blue, given the hyperref settings in force).

Answer 2

For the parentheses, put this in preamble \crefdefaultlabelformat{#2(#1)#3} where #1 stands for the cited item as stated in cleveref documentation

\documentclass[14pt,a4paper]{extreport}
\usepackage[left=2.00cm, right=1.50cm]{geometry}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{lipsum}
\usepackage{hyperref}  
\hypersetup{colorlinks=true,citecolor=red, linkcolor=blue}
\usepackage{cleveref}

\crefdefaultlabelformat{#2(#1)#3}


\begin{document}
\chapter{First  Chapter}\label{ch:chapter 1}
\section{Section One}\label{sec:section one}
\lipsum[1]
\section{Section Two}\label{sec:section two}
\begin{align}
r =& \sqrt{x^2 + y^2}\label{eq:equation 1}\\[2ex]
z =& \sqrt[3]{1 - 2r^2}\label{eq:equation 2}
\end{align}
see \cref{sec:section one} in \cref{ch:chapter 1}\\
\Cref{eq:equation 1} is the governing equations, \cref{eq:equation 2} is the second equation.
\end{document}