I'm trying to make the first page of each chapter in two colors according https://tex.stackexchange.com/a/236952/14423. This works well for the table of contents, but does not work well for the first page of each chapter, as you can see:
Main:
\documentclass[letterpaper,showtrims,draft,11pt]{memoir}
\usepackage[utf8]{inputenc}
\usepackage{lipsum}
\usepackage{tikz}
\newcommand{\amount}{4in} %%<---- adjust
\begin{document}
\frontmatter
\begin{tikzpicture}[remember picture,overlay]
\fill[green] ([yshift=-\amount]current page.north west) rectangle (current page.north east);
\fill[yellow] (current page.south west) rectangle ([yshift=-\amount]current page.north east);
\end{tikzpicture}
\tableofcontents
\include{intro}
\mainmatter
\include{cap1}
\include{cap2}
\backmatter
\include{app}
\end{document}
intro.tex :
\chapter{Introducci\'on}
\begin{tikzpicture}[remember picture,overlay]
\fill[green] ([yshift=-\amount]current page.north west) rectangle (current page.north east);
\fill[yellow] (current page.south west) rectangle ([yshift=-\amount]current page.north east);
\end{tikzpicture}
\lipsum[1-5]
cap1.tex :
\chapter{Cap\'itulo Uno}
\begin{tikzpicture}[remember picture,overlay]
\fill[green] ([yshift=-\amount]current page.north west) rectangle (current page.north east);
\fill[yellow] (current page.south west) rectangle ([yshift=-\amount]current page.north east);
\end{tikzpicture}
\lipsum[1-5]
cap2.tex and app.tex have no lines. Obviously something I'm doing wrong. What is it?