Question: Is there the possiblity to make a color gradient in the rectangular box in the following example from the bottom left to the top right corner (both in linear or radial shape)?

```
\documentclass{article}
\usepackage{tikz}

\usepackage{xcolor}

\definecolor{left} {HTML}{001528}

\begin{document}

  \begin{tikzpicture}[remember picture,overlay]
    \node [rectangle, left color=left, right color=left!30!white, anchor=north, minimum width=\paperwidth, minimum height=5.5cm] (box) at (current page.north){};
  \end{tikzpicture}

\end{document}

```

Thanks for your help!

Answer: 
You can use `shading = axis` and `shading angle=135`

```
\documentclass{article}
\usepackage{tikz}

\definecolor{left} {HTML}{001528}

\begin{document}

  \begin{tikzpicture}[remember picture,overlay]
    \node [shading = axis,rectangle, left color=left, right color=left!30!white,shading angle=135, anchor=north, minimum width=\paperwidth, minimum height=5.5cm] (box) at (current page.north){};
  \end{tikzpicture}
\end{document}

```

![enter image description here](https://i.stack.imgur.com/drXMd.png)
I hope this is what you mean:

![variant shadings and fadings](https://i.stack.imgur.com/mWf2J.png)

```
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{positioning,fadings,through}

\definecolor{left} {HTML}{001528}

\begin{document}

  \begin{tikzpicture}[remember picture,overlay]
    \node [rectangle, left color=left, right color=left!30!white, anchor=north, minimum width=\paperwidth, minimum height=5.5cm] (box) at (current page.north){};
    % manual 181
    \node [rectangle, fill=left!30!white, postaction={path fading=north, fading angle=-45, fill=left}, anchor=north, below=10mm of box, minimum width=\paperwidth, minimum height=5.5cm] (box1) {};
    \begin{scope}
      \clip (box1.south west) +(0,-10mm) coordinate (c1) rectangle +(\paperwidth,-150mm) coordinate (c2);
      \node [inner color=left!30!white, outer color=left, circle through={(c1 |- c2)}] at (c1 -| c2) {};
    \end{scope}
  \end{tikzpicture}

\end{document}

```