How to fix the color regions of this tikz figure?

Question

I am trying to fix the blue region in the figure below but the white part is not completely filled yet.

Here are the following Latex codes for the standalone figure:

 \documentclass{standalone} \usepackage{tikz} \usetikzlibrary{backgrounds,intersections} \usepackage{amsmath} \begin{document} \begin{tikzpicture} % Draw the axes \draw[thin,-] (0,0) -- (4.5,0) node[anchor=north west] {$\psi \gamma_{c}$}; \draw[thin,-] (0,0) -- (0,4.5) node[anchor=south east] {$\phi \gamma_{e}$}; % Define colors \fill[red,opacity=0.3] (0,0) -- (3.18,3.18) -- (4.5,4.5) -- (0,4.5) -- cycle; \fill[blue,opacity=0.3] (0,0) -- (3.18,3.18) -- (5,0) -- cycle; % Draw the diagonal line and annotations \draw (0,0) -- (45:6.2)  node[pos=0.86, above left]{\text{Cash regime}} node[pos=0.55,above left] {$ \begin{aligned} \tau_{x} &= 0 \\ (\phi \gamma_{e} &\geq \psi \gamma_{c}) \end{aligned} $} node[right]{$\zeta = \frac{\gamma_{e}}{\gamma_{c}} = 1$} node[pos=0.30, below right]{\text{CBDC regime}} node[pos=0.55,right] {$ \begin{aligned} \tau_{x} &>0 \\ (\phi \gamma_{e} &< \psi \gamma_{c}) \\ \end{aligned} $} ; \end{tikzpicture}% \end{document}

Any help would be appreciated.

Answer 1

Although it is not terribly visible in the particular example chosen here, it is generally better to fill first and draw afterwards. If you draw the area first and then fill it, the drawn lines will be partly obscured by the fill. Either draw and fill together or draw later.

To see the difference, change the opacities of the fills to one .

This also demonstrates the use of named coordinates to make things more flexible. This also makes it easier to fill the lower blue part.

 \documentclass{standalone} \usepackage{tikz} \usepackage{amsmath} \begin{document} \begin{tikzpicture} % Draw the axes \draw[thin,-] (0,0) coordinate (O)  -- (4.5,0) coordinate (C) node[anchor=north west]  {$\psi \gamma_{c}$}; \draw[thin,-] (O) -- (0,4.5) coordinate (E) node[anchor=south east]  {$\phi \gamma_{e}$}; % Define colors \fill[red!30]   (O) -- (3.18,3.18) coordinate (A) -- (4.5,4.5) coordinate (B) --  (E) -- cycle; \fill[blue!30] (O) -- (B) -- (B |- O) -- cycle; %    Draw the diagonal line and annotations \draw (O) -- (45:6.2)  node[pos=0.86, above left]{\text{Cash regime}} node[pos=0.55,above left] {$ \begin{aligned} \tau_{x} &= 0 \\ (\phi \gamma_{e} &\geq \psi \gamma_{c}) \end{aligned} $} node[right]{$\zeta = \frac{\gamma_{e}}{\gamma_{c}} = 1$} node[pos=0.30, below right]{\text{CBDC regime}} node[pos=0.55,right] {$ \begin{aligned} \tau_{x} &>0 \\ (\phi \gamma_{e} &< \psi \gamma_{c}) \\ \end{aligned} $} ; \end{tikzpicture}% \begin{tikzpicture} % Define colors \fill[red!30] (0,0) coordinate  (O) -- (3.18,3.18) coordinate (A) -- (4.5,4.5) coordinate (B) -- (0,4.5) coordinate (E) -- cycle; \fill[blue!30] (O) -- (B) -- (B |- O) -- cycle; % Draw the axes \draw[thin,-] (O)  -- (4.5,0) coordinate (C) node[anchor=north west]  {$\psi \gamma_{c}$}; \draw[thin,-] (O) -- (E) node[anchor=south east]  {$\phi \gamma_{e}$}; % Draw the diagonal line and annotations \draw (O) -- (45:6.2)  node[pos=0.86, above left]{\text{Cash regime}} node[pos=0.55,above left] {$ \begin{aligned} \tau_{x} &= 0 \\ (\phi \gamma_{e} &\geq \psi \gamma_{c}) \end{aligned} $} node[right]{$\zeta = \frac{\gamma_{e}}{\gamma_{c}} = 1$} node[pos=0.30, below right]{\text{CBDC regime}} node[pos=0.55,right] {$ \begin{aligned} \tau_{x} &>0 \\ (\phi \gamma_{e} &< \psi \gamma_{c}) \\ \end{aligned} $} ; \end{tikzpicture}% \end{document}

Here goes nothing (my images suck right now):

Answer 2

My solution and other answers are welcome! Just extended the diagonal and played with the colors.

 \documentclass{standalone} \usepackage{tikz} \usetikzlibrary{backgrounds,intersections} \usepackage{amsmath} \begin{document} \begin{tikzpicture} % Draw the axes \draw[thin,-] (0,0) -- (4.5,0) node[anchor=north west] {$\psi \gamma_{c}$}; \draw[thin,-] (0,0) -- (0,4.5) node[anchor=south east] {$\phi \gamma_{e}$}; % Define colors \fill[red,opacity=0.3] (0,0) -- (4.5,4.5) -- (0,4.5) -- cycle; \fill[blue,opacity=0.3] (0,0) -- (4.5,4.5) -- (4.5,0) -- cycle; % Draw the diagonal line and annotations \draw (0,0) -- (45:6.35)  node[pos=0.75, above left]{\text{Cash regime}} node[pos=0.50,above left] {$ \begin{aligned} \tau_{x} &= 0 \\ (\phi \gamma_{e} &\geq \psi \gamma_{c}) \end{aligned} $} node[right]{$\zeta = \frac{\gamma_{e}}{\gamma_{c}} = 1$} node[pos=0.25, below right]{\text{CBDC regime}} node[pos=0.50,right] {$ \begin{aligned} \tau_{x} &>0 \\ (\phi \gamma_{e} &< \psi \gamma_{c}) \\ \end{aligned} $} ; \end{tikzpicture}% \end{document}