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.