[Tex/LaTex] Correct order of enlarge, color and bold

Question

What is the right way to have a text enlarged, colored and bold? Non of the following works;

documentclass[a4paper,11pt,fleqn]{book}

% I just write the likely relevant packages.
\usepackage{physics}
\usepackage[hidelinks]{hyperref}
\usepackage{multirow}
\usepackage{color}
\usepackage{booktabs,colortbl}
\mdfdefinestyle{algos}{backgroundcolor=mygrey, linewidth = 1.95pt, frametitlerule=false, frametitlebackgroundcolor=myblue, %
hidealllines=true}

% All colors, perhaps is not the case to be written.
\definecolor{airforceblue}{rgb}{0.36, 0.54, 0.66}

\begin{document}

\large{\color{airforceblue} {\textbf{$N_L(k)$}}}
{\color{airforceblue} \textbf{\large $N_L(k)$}}
{\color{airforceblue} \large{\textbf{$N_L(k)$}}}

\end{document}

Answer 1

Don't use \textbf for math-mode material. Use \mathbf instead; better yet, load the bm package and the \bm ("bold math") macro.

\documentclass{article}
\usepackage{xcolor,bm}
\begin{document}
$N_{abc}$ vs.\ {\Large\color{blue}$\bm{N_{abc}}$}
\end{document}

I don't know how the color "airforceblue" is defined. That's why I used "blue" in the example above. I use \Large instead of \large to make the effect of changing the font size more visually prominent.