Better differentiate highlighted changes (additions or subtractions) within the activity log

Problem to solve

In &896, we performed an audit of GitLab to ensure that we are following standard WCAG standards in terms of Use of Color.

1.4.1 Use of Color: Color is not used as the only visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element. (Level A)

When a user is editing an issue, any additions or subtractions they make are highlighted in either green or red. This may be confusing to people that are visually impaired. I don't feel this is critical as we spell out the changes as well-but worth exploring.

Proposal

I'm not sure yet. Perhaps using colors with better contrast to each other and providing a key? Using outlines or symbols?