\documentclass[border=10pt]{standalone}
\usepackage{pgfplots, amsmath, pgfplotstable}
\usepackage{filecontents}
\usepgfplotslibrary{colorbrewer}
\usepgfplotslibrary{fillbetween}
\definecolor{color1}{rgb}{0,0,0}
\definecolor{color2}{rgb}{0.5,0.5,0.5}
\definecolor{color3}{rgb}{0.5,0.5,0.5}


\pgfplotsset{every axis plot/.append style={line width=1pt},compat=1.8}

\begin{document}

\begin{tikzpicture}
\begin{axis}[
ylabel=$K_b(t)$,
xlabel= $t/t_{\rm s}$,
width = 5cm,
height = 4.5cm,
cycle list/Paired-5,
%cycle list name = Paired-10,
minor tick style={draw=none},
ymax=11]

\addplot+[thick,no marks,x filter/.code={\pgfmathparse{#1*1/10}\pgfmathresult}] table[x=x,y=y] {data_K0.txt};
\addplot [name path=upper,draw=none,x filter/.code={\pgfmathparse{#1*1/10}\pgfmathresult}] table[mark options={fill=black,scale=2}, x=x,y expr=\thisrow{y}+\thisrow{err}] {data_K0.txt};
\addplot [name path=lower,draw=none,x filter/.code={\pgfmathparse{#1*1/10}\pgfmathresult}] table[mark options={fill=black,scale=2}, x=x,y expr=\thisrow{y}-\thisrow{err}] {data_K0.txt};
\addplot [fill=black!10] fill between[of=upper and lower];

\addplot+[thick,no marks,x filter/.code={\pgfmathparse{#1*1/10}\pgfmathresult}] table[x=x,y=y] {data_K25.txt};
\addplot [name path=upper,draw=none,x filter/.code={\pgfmathparse{#1*1/10}\pgfmathresult}] table[mark options={fill=black,scale=2}, x=x,y expr=\thisrow{y}+\thisrow{err}] {data_K25.txt};
\addplot [name path=lower,draw=none,x filter/.code={\pgfmathparse{#1*1/10}\pgfmathresult}] table[mark options={fill=black,scale=2}, x=x,y expr=\thisrow{y}-\thisrow{err}] {data_K25.txt};
\addplot [fill=black!10] fill between[of=upper and lower];

\addplot+[thick,no marks,x filter/.code={\pgfmathparse{#1*1/10}\pgfmathresult}] table[x=x,y=y] {data_K50.txt};
\addplot [name path=upper,draw=none,x filter/.code={\pgfmathparse{#1*1/10}\pgfmathresult}] table[mark options={fill=black,scale=2}, x=x,y expr=\thisrow{y}+\thisrow{err}] {data_K50.txt};
\addplot [name path=lower,draw=none,x filter/.code={\pgfmathparse{#1*1/10}\pgfmathresult}] table[mark options={fill=black,scale=2}, x=x,y expr=\thisrow{y}-\thisrow{err}] {data_K50.txt};
\addplot [fill=black!10] fill between[of=upper and lower];

\addplot+[thick,no marks,x filter/.code={\pgfmathparse{#1*1/10}\pgfmathresult}] table[x=x,y=y] {data_K75.txt};
\addplot [name path=upper,draw=none,x filter/.code={\pgfmathparse{#1*1/10}\pgfmathresult}] table[mark options={fill=black,scale=2}, x=x,y expr=\thisrow{y}+\thisrow{err}] {data_K75.txt};
\addplot [name path=lower,draw=none,x filter/.code={\pgfmathparse{#1*1/10}\pgfmathresult}] table[mark options={fill=black,scale=2}, x=x,y expr=\thisrow{y}-\thisrow{err}] {data_K75.txt};
\addplot [fill=black!10] fill between[of=upper and lower];

\addplot+[thick,no marks,x filter/.code={\pgfmathparse{#1*1/10}\pgfmathresult}] table[x=x,y=y] {data_K100.txt};
\addplot [name path=upper,draw=none,x filter/.code={\pgfmathparse{#1*1/10}\pgfmathresult}] table[mark options={fill=black,scale=2}, x=x,y expr=\thisrow{y}+\thisrow{err}] {data_K100.txt};
\addplot [name path=lower,draw=none,x filter/.code={\pgfmathparse{#1*1/10}\pgfmathresult}] table[mark options={fill=black,scale=2}, x=x,y expr=\thisrow{y}-\thisrow{err}] {data_K100.txt};
\addplot [fill=black!10] fill between[of=upper and lower];

\end{axis}
\end{tikzpicture}
\end{document}