What's the problem this feature will solve?

The Full diff that pytest shows in -vv mode is very red and hard to read. Missing, common and extra entries all have the same color!

For reference, this is what it looks like:

Describe the solution you'd like

This diff is the same kind of diff that people might already be familiar with, typically running git diff. Those are often colored already. There is a pygments lexer for parsing such diffs.

As such, I would propose to enhance the coloring of those diffs when pygments is install, which would give something like:

Which I believe is much easier to read and spot differences.

I'd be happy to implement the solution if you would be willing to accept such a change.

This might require passing the terminal writer into the tooling that provides the diff to check whether colors should be enabled however.