Set signal curve and legend text color to gray.
Summary: Set signal curve and legend text color to gray.
Test Plan: Manually
Reviewers: floca, O3 MITK Reviewer Group II, s434n
Reviewed By: floca, O3 MITK Reviewer Group II, s434n
Subscribers: s434n
Differential Revision: https://phabricator.mitk.org/D978