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It is not possible to change/customize QA check colors in XTM Workbench in any way.
Does XTM Cloud have any auto-correct feature in XTM Workbench?
XTM Cloud does not have any built-in auto-correct feature in XTM Workbench. Any language errors are highlighted according to the error type. Make sure you have got acquainted with the following articles on how to proofread the target segments with regard to language: