在列表环境中使用颜色如何改变页面其余部分的间距？

Question

以下 MWE 在页面上适合 5 个引用。一旦我取消注释颜色命令 ( \myblue)，它就只能容纳 4 个，其他一切都没有改变。

相关：我还有一个未解决的问题是为什么包裹在卷曲空格中的彩色换行符会占用空间？这个与段落开头（或结尾）的颜色有关；在这里，我在环境内的段落内使用颜色……

\documentclass{article}
\usepackage{xcolor}
\def\mysmall{\trivlist\item\small}
\def\endmysmall{\endtrivlist}
% \newcommand{\myblue}{\color{blue}}
\providecommand{\myblue}{}

\usepackage{lipsum}
\begin{document}
    \lipsum[1]

    \section{Conclusion}
    \lipsum[6]

    \begin{mysmall}
        Black and black and black and black and black and black and black and \myblue{}blue: \lipsum[4]
    \end{mysmall}

    \begin{thebibliography}{3}
        \small
        \bibitem{Bla}Bla and bla and bla and bla and bla and bla and bla and bla and bla and bla and bla
        \bibitem{Bla}Bla and bla and bla and bla and bla and bla and bla and bla and bla and bla and bla
        \bibitem{Bla}Bla and bla and bla and bla and bla and bla and bla and bla and bla and bla and bla
        \bibitem{Bla}Bla and bla and bla and bla and bla and bla and bla and bla and bla and bla and bla
        \bibitem{Bla}Bla and bla and bla and bla and bla and bla and bla and bla and bla and bla and bla
        \bibitem{Bla}Bla and bla and bla and bla and bla and bla and bla and bla and bla and bla and bla
    \end{thebibliography}
\end{document}

我已经能够进一步将我的问题最小化为这个MWE：

\documentclass{article}
\usepackage{color}
\newcommand{\blue}{}
% \renewcommand{\blue}{\color{blue}}
\begin{document}
    \begin{itemize}
        \item Black and \blue{}blue.
    \end{itemize}

    \section{This moves down when the above is blue.}
\end{document}