$ hostname
cambridge

ubuntu@ip-172-31-12-203:~$ hostname
ip-172-31-12-203

\documentclass[a4paper]{article}
\usepackage{tikz}

\newcounter{rowno}
\setcounter{rowno}{-1}
%\stepcounter{rowno}
%\therowww
\begin{document}
\def\Rows{7}
\foreach \n in {1,...,\Rows}{%%
%\noindent\n,~
\foreach \col in {1,...,\Rows}{%
\pgfmathsetmacro\filled{\col<=\n ? 1 : 0}
\pgfmathsetmacro\first{\col==\n ? 1 : 0}
\noindent\ifnum\filled=1 \stepcounter{rowno}%
         \ifnum\first=1 \col f, \therowno%
            \else  \col,\therowno\fi%
           ~~~ \else  x\fi
}\\%
}%%
\end{document}

\documentclass[a4paper]{article}

\begin{tabular}{c c c c}
a & 1 & 2 & 3 \\
a
\foreach \k in {1,2,3}{& \k}
\end{tabular}

\end{document}

\makeatletter
\patchcmd\reset@color{\beamerorig@reset@color}{\beamerorig@reset@color\color{.}}{}{\fail}
\makeatother

\makeatletter
\patchcmd\reset@color{\beamerorig@reset@color\pgfsys@color@unstacked}{\beamerorig@reset@color\color{.}\pgfsys@color@unstacked}{}{\fail}
\makeatother

\documentclass[xcolor={rgb}]{beamer}
\setbeamercovered{transparent}
\beamertemplatenavigationsymbolsempty
\setbeamersize{text margin left=10mm,text margin right=5mm}
\setbeamertemplate{frametitle}[default][center]
\usepackage{mathtools}
\usepackage{bm}
\newcommand{\var}[1]{\operatorname{var}{#1}}
\newcommand{\E}{\mathbb{E}}
\newcommand{\norm}[1]{\left\lVert#1\right\rVert}

\makeatletter
\patchcmd\reset@color{\beamerorig@reset@color\pgfsys@color@unstacked}{\beamerorig@reset@color\color{.}\pgfsys@color@unstacked}{}{\fail}

\documentclass{article}
\usepackage{xcolor}
\begin{document}
 \color{red} outside

 \begingroup
  \xglobal\blendcolors{!20!white}inside \color{blue} mixin
 \endgroup

  no mixing outside \color{.} now mixin outside
\end{document}

\documentclass[11pt]{article}

\usepackage{fontspec}
\setmainfont{Charis SIL}[]

\begin{document}

abc

\end{document}