Defining a header with background color in Latex

Question

For a small project I'm trying something that feels as if it should be peanut, but au contraire (Hey, that's french, never thought I'd remember some parts of that. anyway...).

The thing is, I want a latex layout where the header and footer span the entire pagewidth and have a background color, and also can have some elements on the left, center, or right (like with fancyhdr). The thing is, I simply cannot get this to work without screwing up the rest of the layout.

edit: added example.

Here's an example of what I have tried. The header is shown incorrectly since the background doesn't span the whole width of the page. The footer is not shown at all.

\documentclass[10pt,a4paper,notitlepage]{article}
\usepackage[latin1]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{graphicx}
\usepackage[usenames,dvipsnames]{color}
\usepackage{fancyhdr}
\usepackage{calc}
\usepackage{tikz}
\usepackage[landscape, top=0cm, bottom=3cm]{geometry}

\definecolor{logoGreen}{RGB}{218,226,87}

\newcommand{\HBG}{
    \begin{tikzpicture}[remember picture,overlay]
        \node[yshift=-2cm] at (current page.north west)
        {
            \begin{tikzpicture}[remember picture, overlay]
                \draw[fill=logoGreen] (0,0) rectangle (\paperwidth,2cm);
            \end{tikzpicture}
        };
    \end{tikzpicture}
}

\fancyhead{}
\fancyhead[L]{\HBG}
\fancyhead[C]{\includegraphics[height=1.2cm]{"img/headerimg"}}

\fancyfoot[C]{\includegraphics[height=1.2cm]{"img/footerimg"}}

\fancyhfoffset[]{1in+\hoffset+\oddsidemargin}

\renewcommand{\headrulewidth}{0pt}
\renewcommand{\footrulewidth}{0pt}

\headheight 3cm
\footskip -2cm

\pagestyle{fancy}

\begin{document}
\section{first section}
content 
\end{document}

Answer 1

You can use TikZ to position coloured boxes absolutely on the page. See an example here.

This example includes usage of \thechapter, so you can probably go on from there.