How to change color and transparency of arrows in tikz?

Question

I have the following code.

\documentclass[a4paper]{article}
\usepackage{tikz}
\usetikzlibrary{cd,shapes,arrows.meta}
\begin{document}
\begin{tikzcd}[cells={nodes={scale=0.5,draw=gray,thin,rectangle,rounded corners}},
row sep=normal,column sep=scriptsize]
&1,\color{red}2  \ar[r,"\lambda",shift left]\ar[ld,"\bar{p}\mu",swap,blue] 
&   2,\color{red}2 \ar[r,"\lambda",shift left] \ar[l,"\mu",shift left]  
&   |[draw=none]| \cdots \ar[r,"\lambda",shift left] \ar[l,"\mu",shift left] 
&  .,\color{red}2  \ar[l,"\mu",shift left] \\
% 
0,\color{cyan}0 \ar[r,"\lambda",shift left] 
&   1,\color{cyan}0 \ar[r,"\lambda",shift left] \ar[l,"\eta",shift left] \ar[u,"\phi",swap] 
&   2,\color{cyan}0 \ar[r,"\lambda",shift left] \ar[l,"q\eta",shift left] \ar[u,"\phi",swap] 
\ar{lu}[description]{\bar{q}\eta}
&   |[draw=none]| \cdots \ar[r,"\lambda",shift left] \ar[l,"q\eta",shift left] 
\ar{lu}[description]{\bar{q}\eta} 
& .,\color{cyan}0 \ar[l,"q\eta",shift left]\ar[u,"\phi",shift left]
\ar{lu}[description]{\bar{q}\eta} 
\end{tikzcd}
\end{document}

which generates the figure

I want to change the colors of the diagonal arrows and the head shape. Also to make the $\bar{q}\eta$ fill transparent so that some part of the side symbols will not be overlapped. How to do that without changing the scale of the plot?

Answer 1

If you do not want to change the scaling, the labels will get very close which is not very beautiful in my opinion. As I have stated in my comment above, you can not just make the fill of the description transparent. This would result in something similar to no fill at all.

The trick I use below is to change the order of drawing. If you do the diagonals first and then the lower arrows, you will get a correct overlapping. At least I hope this is what you want.

The other questions are all treated on this site already and are therefore not explained further.

% arara: pdflatex

\documentclass[a4paper]{article}
\usepackage{tikz-cd}

\begin{document}
\begin{tikzcd}[%
    ,cells={nodes={scale=0.5,draw=gray,thin,rectangle,rounded corners}}
    ,row sep=normal
    ,column sep=scriptsize
    ,every arrow/.append style=-latex]
        & 1,\color{red}2  \ar[r,"\lambda",shift left]\ar[ld,"\bar{p}\mu",swap,blue]\arrow[blue,latex-]{dr}[description]{\bar{q}\eta} 
        & 2,\color{red}2 \ar[r,"\lambda",shift left] \ar[l,"\mu",shift left] \arrow[blue,latex-]{dr}[description]{\bar{q}\eta} 
        & |[draw=none]| \cdots \ar[r,"\lambda",shift left] \ar[l,"\mu",shift left] \arrow[blue,latex-]{dr}[description]{\bar{q}\eta}
        & .,\color{red}2  \ar[l,"\mu",shift left] \\
        0,\color{cyan}0 \ar[r,"\lambda",shift left] 
        &   1,\color{cyan}0 \ar[r,"\lambda",shift left] \ar[l,"\eta",shift left] \ar[u,"\phi",swap] 
        &   2,\color{cyan}0 \ar[r,"\lambda",shift left] \ar[l,"q\eta",shift left] \ar[u,"\phi",swap]
        &   |[draw=none]| \cdots \ar[r,"\lambda",shift left] \ar[l,"q\eta",shift left]  
        & .,\color{cyan}0 \ar[l,"q\eta",shift left]\ar[u,"\phi",shift left]
\end{tikzcd}
\end{document}