change comma to colon after (year) using biblatex.sty

Question

My tags are:

\documentclass{book}
\usepackage[american]{babel}
\usepackage{csquotes}
\usepackage[maxbibnames=99,%style=numeric,
style=ext-numeric,%
citestyle=numeric,sorting=nyt,sortcites=true,autopunct=true,autolang=hyphen,hyperref=true,abbreviate=false,backref=true,backend=biber]{biblatex}
\usepackage{filecontents}
\begin{filecontents*}{\jobname.bib}
@article{acerbi2014origins,
  title={On the Origins of Suboptimality in Human Probabilistic Inference},
  author={Acerbi, Luigi and Vijayakumar, Sethu and Wolpert, Daniel M.},
  journal={PLoS Computational Biology},
  volume={10},
  number={6},
  pages={e1003661},
  year={2014},
  publisher={Public Library of Science San Francisco, USA}
}
}
\end{filecontents*}
\addbibresource{\jobname.bib}
\begin{document}
\renewbibmacro*{in:}{%
  \setunit{\addcomma\space}%
  \ifentrytype{article}
    {}
    {\printtext{%
       \bibstring{in}\intitlepunct}}}
\newcommand{\aftertitlepunct}{\addperiod\space}
\newcommand{\afterbooktitlepunct}{\aftertitlepunct}
\newcommand*{\aftermaintitlepunct}{\aftertitlepunct}
\renewcommand*{\volnumdelim}{\addcomma\space}
\DeclareFieldFormat[article,periodical]{number}{\bibsstring{number}~#1}
\renewbibmacro*{title}{%
  \ifboolexpr{
    test {\iffieldundef{title}}
    and
    test {\iffieldundef{subtitle}}
  }
    {}
    {\printtext[title]{%
       \printfield[titlecase:title]{title}%
       \setunit{\subtitlepunct}%
       \printfield[titlecase:title]{subtitle}}%
     \setunit{\titleaddonpunct}}%
  \printfield{titleaddon}%
  \ifboolexpr{
    test {\iffieldundef{title}}
    and
    test {\iffieldundef{subtitle}}
  }
    {}
    {\printunit{\aftertitlepunct}}}
\renewbibmacro*{booktitle}{%
  \ifboolexpr{
    test {\iffieldundef{booktitle}}
    and
    test {\iffieldundef{booksubtitle}}
  }
    {}
    {\printtext[booktitle]{%
       \printfield[titlecase:booktitle]{booktitle}%
       \setunit{\subtitlepunct}%
       \printfield[titlecase:booktitle]{booksubtitle}}%
     \setunit{\titleaddonpunct}}%
  \printfield{booktitleaddon}%
  \ifboolexpr{
    test {\iffieldundef{booktitle}}
    and
    test {\iffieldundef{booksubtitle}}
  }
    {}
    {\printunit{\afterbooktitlepunct}}}
\nocite{*}
\printbibliography
\end{document}

It produced the output as:

I need to change the marked comma to colon, please advise...