Fix cycling through colors in ray path plots, now also fixes cartesia…

[megies]

What does this PR do?

Fixes #2470.. again! Now also for cartesian plots..

Why was it initiated? Any relevant Issues?

See #2470 and #2478

PR Checklist

• Correct base branch selected? master for new features, maintenance_... for bug fixes
• This PR is not directly related to an existing issue (which has no PR yet).
• If the PR is making changes to documentation, docs pages can be built automatically.
  Just add the "build_docs" tag to this PR.
  Docs will be served at docs.obspy.org/pr/{branch_name} (do not use master branch).
  Please post a link to the relevant piece of documentation.
• If all tests including network modules (e.g. clients.fdsn) should be tested for the PR,
  just add the "test_network" tag to this PR.
• All tests still pass.
• Any new features or fixed regressions are covered via new tests.
• Any new or changed features are fully documented.
• Significant changes have been added to CHANGELOG.txt .
• First time contributors have added your name to CONTRIBUTORS.txt .
• If the changes affect any plotting functions you have checked that the plots
  from all the CI builds look correct. Add the "upload_plots" tag so that plotting
  outputs are attached as artifacts.
• Add the "ready for review" tag when you are ready for the PR to be reviewed.

[megies]

@jrekoske can you check if this works for you and maybe also check if other plots still work when docs build is done and can be seen at https://docs.obspy.org/pr ?

[jrekoske]

@megies Looks good thanks!