\documentclass[tikz]{standalone}
%
% This is a direct copy of the codes in section 2.9 of the package
% documentation (See page 45) https://mirrors.tuna.tsinghua.edu.cn/CTAN/graphics/pgf/contrib/pgfgantt/pgfgantt.pdf
% except the color setting
\usepackage{pgfgantt}
\usepackage{xcolor}
\usepackage[utf8]{inputenc}
\definecolor{barblue}{RGB}{153,204,254}
\definecolor{groupblue}{RGB}{51,102,254}
\definecolor{linkred}{RGB}{165,0,33}
\begin{document}
\begin{ganttchart}[
y unit title=0.4cm,
y unit chart=0.5cm,
vgrid,
time slot format=isodate-yearmonth,
compress calendar,
title/.append style={draw=none, fill=barblue},
title label font=\sffamily\bfseries\color{white},
title label node/.append style={below=-1.6ex},
title left shift=.05,
title right shift=-.05,
title height=1,
bar/.append style={draw=none, fill=groupblue},
bar height=.6,
bar label font=\normalsize\color{black!50},
group right shift=0,
group top shift=.6,
group height=.3,
group peaks height=.2,
bar incomplete/.append style={fill=green}
]{2010-09}{2011-12}
\gantttitlecalendar{year}\\
\ganttbar[
progress=100,
bar progress label font=\small\color{barblue},
bar progress label node/.append style={right=4pt},
bar label font=\normalsize\color{barblue},
name=pp
]{Preliminary Project}{2010-09}{2010-12} \\
\ganttset{progress label text={}, link/.style={black, -to}}
\ganttgroup{Objective 1}{2011-01}{2011-12} \\
\ganttbar[progress=4, name=T1A]{Task A}{2011-01}{2011-06} \\
\ganttlinkedbar[progress=0]{Task B}{2011-07}{2011-12} \\
\ganttgroup{Objective 2}{2011-01}{2011-12} \\
\ganttbar[progress=15, name=T2A]{Task A}{2011-01}{2011-09} \\
\ganttlinkedbar[progress=0]{Task B}{2011-10}{2011-12} \\
\ganttgroup{Objective 3}{2011-05}{2011-08} \\
\ganttbar[progress=0]{Task A}{2011-05}{2011-08}
\ganttset{link/.style={green}}
\ganttlink[link mid=.4]{pp}{T1A}
\ganttlink[link mid=.159]{pp}{T2A}
\end{ganttchart}
\end{document}