enable fill between two lines in y direction only within intersection part

This code snippet will plot two lines:

import plotly.graph_objs as go

anchor_rate = [1000, 1660.89, 3220.62, 5927.36]
anchor_psnr = [31.799098, 34.155477, 36.053423, 36.5]

tested_rate = [752.33,1608.90,3114.10,5685.72]
tested_psnr = [31.336015,33.752160,35.730303,37.200365]

fig = go.Figure()

fig.add_trace(go.Scatter(
    x=anchor_rate,
    y=anchor_psnr,
))

fig.add_trace(go.Scatter(
    x=tested_rate,
    y=tested_psnr,
))

fig.show()

This is the plot:

How to fill between two lines in y direction only within intersection part, like this? And how can fill them with different colors?

In summary, two questions:

1. How to fill between two lines in y direction only within intersection part?
2. And how can fill them with different colors?

Start by reproducing the provided Python example with two go.Scatter traces and compare it with the requested intersection-only plot. Investigate the existing Scatter fill behavior and determine how the two questions—restricted filling and different colors—should be supported; done means both requested outcomes are demonstrated or specified clearly.