How to change the colormap in quiver?

Question

I have made this quiver plot with pgfplots:

\documentclass{standalone}

\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{compat = newest}
\usepgfplotslibrary{colormaps}

\begin{document}
    \def\modulus{sqrt(x^2+y^2)}
    \begin{tikzpicture}
        \begin{axis}[
            xmin = -4, xmax = 4,
            ymin = -4, ymax = 4,
            zmin = 0, zmax = 1,
            axis equal image,
            xtick distance = 1,
            ytick distance = 1,
            view = {0}{90},
            scale = 1.5,
            colorbar
        ]
            \addplot3[
                point meta = {\modulus},
                quiver = {
                    u = {-y/\modulus},
                    v = {x/\modulus},
                    scale arrows = 0.25,
                },
                quiver/colored = {mapped color},
                samples = 20,
                - stealth,
                domain = -4:4,
                domain y = -4:4,
            ] {0};
        \end{axis}
    \end{tikzpicture}
\end{document}

I would like to change the colormap to greenyellow, hot, violet or any other colormap.

Answer 1

With the help of \pgfplotsset{colormap=...} you can define your own color map colors. \pgfplotsset{colormap={CM}{rgb255(1)=(4,50,4) color(5)=(yellow)}} will for example give a dark green to yellow gradient:

\documentclass{standalone}

\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{compat = newest}
\usepgfplotslibrary{colormaps}


\pgfplotsset{colormap={CM}{rgb255(1)=(4,50,4) color(5)=(yellow)}}

\begin{document}
    \def\modulus{sqrt(x^2+y^2)}
    \begin{tikzpicture}
        \begin{axis}[
            xmin = -4, xmax = 4,
            ymin = -4, ymax = 4,
            zmin = 0, zmax = 1,
            axis equal image,
            xtick distance = 1,
            ytick distance = 1,
            view = {0}{90},
            scale = 1.5,
            colorbar
        ]
            \addplot3[
                point meta = {\modulus},
                quiver = {
                    u = {-y/\modulus},
                    v = {x/\modulus},
                    scale arrows = 0.25,
                },
                quiver/colored = {mapped color},
                samples = 20,
                - stealth,
                domain = -4:4,
                domain y = -4:4,
            ] {0};
        \end{axis}
    \end{tikzpicture}
\end{document}

Please note that using the above code, the new color map will be used as the default. If you want to only change the color map of a single plot, you can either use the above shown definition inside of the corrensonding tikzpicture or use the colormap name option as shown in the following exmple:

 \documentclass{article}

\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{compat = newest}
\usepgfplotslibrary{colormaps}

\pgfplotsset{colormap={mymapgreen}{rgb255(1)=(4,50,4) color(5)=(yellow)}}
\pgfplotsset{colormap={mymapviolet}{rgb255(1)=(150,120,175) rgb255(5)=(81,6,60)}}


\begin{document}
    \def\modulus{sqrt(x^2+y^2)}
    \begin{tikzpicture}

        \begin{axis}[
            xmin = -4, xmax = 4,
            ymin = -4, ymax = 4,
            zmin = 0, zmax = 1,
            axis equal image,
            xtick distance = 1,
            ytick distance = 1,
            view = {0}{90},
            scale = 1.5,
            colorbar,
            colormap name ={mymapgreen} %<-------
        ]
            \addplot3[
                point meta = {\modulus},
                quiver = {
                    u = {-y/\modulus},
                    v = {x/\modulus},
                    scale arrows = 0.25,
                },
                quiver/colored = {mapped color},
                samples = 20,
                - stealth,
                domain = -4:4,
                domain y = -4:4,
            ] {0};
        \end{axis}
    \end{tikzpicture}



        \begin{tikzpicture}
        \begin{axis}[
            xmin = -4, xmax = 4,
            ymin = -4, ymax = 4,
            zmin = 0, zmax = 1,
            axis equal image,
            xtick distance = 1,
            ytick distance = 1,
            view = {0}{90},
            scale = 1.5,
            colorbar, 
            colormap name ={mymapviolet} %<-------
        ]
            \addplot3[
                point meta = {\modulus},
                quiver = {
                    u = {-y/\modulus},
                    v = {x/\modulus},
                    scale arrows = 0.25,
                },
                quiver/colored = {mapped color},
                samples = 20,
                - stealth,
                domain = -4:4,
                domain y = -4:4,
            ] {0};
        \end{axis}
    \end{tikzpicture}
\end{document}

Using colormap name= you can of course also chose from the following predefined color maps: viridis, hot, hot2, jet, blackwhite, bluered, cool, greenyellow, redyellow, and violet.

For more information, you mght be interested in section "4.7 Markers, Linestyles, (Background) Colors and Colormaps" (especially in subsection "4.7.6 Color Maps", currently starting on page 192) of the pgfplots manual.