I have been trying to draw this but unable to color it or create the grids.. can anyone help me?

[![solid](https://i.stack.imgur.com/hc0zB.png)](https://i.stack.imgur.com/hc0zB.png)

This is my MWE:

```
\documentclass[tikz]{standalone}

\begin{document}
    \begin{tikzpicture}
        % Arc
        \draw(0.66,1.26) arc (37:90:0.8 and 1.8);% left arc
        \draw(3.3,1.3) arc (37:90:-0.8 and 1.8);% left arc

        % Lines
        \draw (2,3) -- (0,2);% line 1
        \draw (2,3) -- (4,2);% line 2
        \draw (2,2) -- (0.66,1.3);% line 3
        \draw (2,2) -- (3.3,1.3);% line 4
        \draw (0,2) -- (0,1.4);% line 5
        \draw (0,1.4) -- (0.66,1.3);% line 6
        \draw (4,2) -- (4,1.5);% line 7
        \draw (4,1.5) -- (3.3,1.3);% line 8

        \draw (-1.25,1.5) node {$\phi$};

    \end{tikzpicture}
\end{document}

```