\documentclass[11pt]{article}
\usepackage[svgnames]{xcolor}
\usepackage[english]{babel}
\usepackage[latin1]{inputenc}
\usepackage{amsfonts, amssymb, amsmath, amsthm,subeqnarray,dsfont}
\usepackage{multirow}
\usepackage{pgf,tikz,setspace}
\usepackage{setspace}
\usepackage[margin=2.5cm]{geometry}
\usepackage{natbib}
\usepackage{hhline}
\usepackage{url}
\usepackage{float,graphicx}
\usepackage[labelfont=bf]{caption}
\usepackage{subcaption}
\usepackage[pagebackref=true]{hyperref}
\usepackage{todonotes}
\usepackage{pgfplots}
\usepackage{comment}
\usepackage{pdflscape}
\usepackage{placeins}
\hypersetup{
    colorlinks=true,       % false: boxed links; true: colored links
    linkcolor=DarkBlue,          % color of internal links
    citecolor=DarkBlue,        % color of links to bibliography
    filecolor=DarkBlue,      % color of file links
    urlcolor=DarkBlue           % color of external links
}

\newcommand*{\blue}{\textcolor{blue}}
\newcommand*{\red}{\textcolor{red}}


\begin{document}

\spacing{1}

\vskip 15pt

\pgfmathdeclarefunction{gauss}{2}{%
  \pgfmathparse{1/(#2*sqrt(2*pi))*exp(-((x-#1)^2)/(2*#2^2))}%
}

    \begin{tikzpicture}[scale=0.75]
        \begin{axis}[
            ybar,
            bar width=8,
            xlabel={Realized Profit at $a_1=4.9 \quad (a_2=5)$},
            ylabel={Probability},
            ymin=0,
            ymax=0.8,
            xtick={0,0.9,4.9},
            xticklabels={$0$, $0.9$, $4.9$},
            ]

            \addplot[fill=blue!30] coordinates {
                (0, 0.7)
                (0.9, 0.21)
                (4.9, 0.08)
            };

             \addplot[fill=red!30] coordinates {
                (0, 0.7)
                (0.9, 0.15)
                (4.9, 0.15)
            };

\node[above, font=\footnotesize] at (axis cs:2.4, 0.7) {\textbf{Variance Profit No adv. Sel.$=2.93$}};
\node[above, font=\footnotesize] at (axis cs:2.4, 0.6) {\textbf{Variance Profit Ad Sel.$=1.78$}};
        \end{axis}
    \end{tikzpicture}

\end{document} 