[Tex/LaTex] tikz mindmap looks bad

Question

Following Sigur's suggestion in a comment I increased the level distances so that the node separation looks reasonable, but the image I get is still weird (the transitions continue to have an undesired orange color):

Expected result would be more like this:

MWE (from https://www.sharelatex.com/blog/2013/09/04/tikz-series-pt5.html, and my example is compiled on sharelatex at https://www.sharelatex.com/project/52d47f206202b37430000733).

\documentclass[article, a4paper, 12pt, oneside]{memoir}

\usepackage{tikz}
\usetikzlibrary{mindmap}
\pagestyle{empty}
\begin{document}
\begin{tikzpicture}[grow cyclic, text width=2cm, align=flush center, every node/.style=concept, concept color=orange!40,
level 1/.style={level distance=6cm,sibling angle=90},
level 2/.style={level distance=4cm,sibling angle=45}]

\node{ShareLaTeX Tutorial Videos}
   child [concept color=blue!30] { node {Beginners Series}
        child { node {First Document}}
        child { node {Sections and Paragraphs}}
        child { node {Mathematics}}
        child { node {Images}}
        child { node {bibliography}}
        child { node {Tables and Matrices}}
        child { node {Longer Documents}}
    }
    child [concept color=yellow!30] { node {Thesis Series}
        child { node {Basic Structure}}
        child { node {Page Layout}}
        child { node {Figures, Subfigures and Tables}}
        child { node {Biblatex}}
        child { node {Title Page}}
    }
    child [concept color=teal!40]  { node {Beamer Series}
        child { node {Getting Started}}
        child { node {Text, Pictures and Tables}}
        child { node {Blocks, Code and Hyperlinks}}
        child { node {Overlay Specifications}}
        child { node {Themes and Handouts}}
    }
    child [concept color=purple!50] { node {TikZ Series}
        child { node {Basic Drawing}}
        child { node {Geogebra}}
        child { node {Flow Charts}}
        child { node {Circuit Diagrams}}
        child [concept color=green!40]  { node {Mind Maps}}
    };

\end{tikzpicture}
\end{document}

Answer 1

The reason that the transition colors are "wrong" is because you did not use the mindmap optional argument to the tikzpicture environment.

Here is how I found the problem, by playing with a minimal example to try to understand what went wrong. The following example is based on the example in chapter 6 of the PGF/TikZ manual version 3.0.0.

---

Without mindmap optional argument:

\documentclass[margin=2mm]{standalone}

\usepackage{tikz}
\usetikzlibrary{mindmap}

\begin{document}
\begin{tikzpicture}[
    %mindmap,                   %% NOTE: mindmap optional argument commented out!
    every node/.style=concept,
    concept color=black!20,
    grow cyclic,
    level 1/.append style={level distance=4.5cm,sibling angle=90},
    level 2/.append style={level distance=3cm,sibling angle=45}
    ]
  \node [root concept] {Computational Complexity} % root
    child [concept color=red] { node {Computational Problems}
      child { node {Problem Measures} } 
      child { node {Problem Aspects} }
    }
    child [concept color=blue] { node {Computational Models}
      child { node {Turing Machines} }
      child { node {Random-Access Machines} }
    };
\end{tikzpicture}
\end{document}

---

With mindmap optional argument:

\documentclass[margin=2mm]{standalone}

\usepackage{tikz}
\usetikzlibrary{mindmap}

\begin{document}
\begin{tikzpicture}[
    mindmap,
    every node/.style=concept,
    concept color=black!20,
    grow cyclic,
    level 1/.append style={level distance=4.5cm,sibling angle=90},
    level 2/.append style={level distance=3cm,sibling angle=45}
    ]
  \node [root concept] {Computational Complexity} % root
    child [concept color=red] { node {Computational Problems}
      child { node {Problem Measures} } 
      child { node {Problem Aspects} }
    }
    child [concept color=blue] { node {Computational Models}
      child { node {Turing Machines} }
      child { node {Random-Access Machines} }
    };
\end{tikzpicture}
\end{document}

---

Fixed mindmap:

I needed to increase the dimensions of the paper, increase the level distances to make the circles not overlap, and increase the text width to improve the text alignment.

\documentclass[article, 12pt, oneside]{memoir}

\usepackage[a2paper]{geometry}
\usepackage{tikz}
\usetikzlibrary{mindmap}
\pagestyle{empty}
\begin{document}
\begin{tikzpicture}[
    mindmap,
    grow cyclic, text width=4cm, align=flush center,
    every node/.style={concept},
    concept color=orange!40,
    level 1/.style={level distance=10cm,sibling angle=90},
    level 2/.style={level distance=6cm,sibling angle=45}]

\node [root concept] {ShareLaTeX Tutorial Videos}
   child [concept color=blue!30] { node {Beginners Series}
        child { node {First Document}}
        child { node {Sections and Paragraphs}}
        child { node {Mathematics}}
        child { node {Images}}
        child { node {bibliography}}
        child { node {Tables and Matrices}}
        child { node {Longer Documents}}
    }
    child [concept color=yellow!30] { node {Thesis Series}
        child { node {Basic Structure}}
        child { node {Page Layout}}
        child { node {Figures, Subfigures and Tables}}
        child { node {Biblatex}}
        child { node {Title Page}}
    }
    child [concept color=teal!40]  { node {Beamer Series}
        child { node {Getting Started}}
        child { node {Text, Pictures and Tables}}
        child { node {Blocks, Code and Hyperlinks}}
        child { node {Overlay Specifications}}
        child { node {Themes and Handouts}}
    }
    child [concept color=purple!50] { node {TikZ Series}
        child { node {Basic Drawing}}
        child { node {Geogebra}}
        child { node {Flow Charts}}
        child { node {Circuit Diagrams}}
        child [concept color=green!40]  { node {Mind Maps}}
    };
\end{tikzpicture}
\end{document}