Remove alias `colour` for `color`

Summary

This pull request removes the alias colour for color.

[ ] If code changes were made then they have been tested.
- [x] I have updated the documentation to reflect the changes.
[ ] This PR fixes an issue.
[ ] This PR adds something new (e.g. new method or parameters).
[x] This PR is a breaking change (e.g. methods or parameters removed/renamed)
[ ] This PR is not a code change (e.g. documentation, README, ...)