Fix user/community instance colour not being applied properly

[hjiangsu]

Pull Request Description

This PR fixes an issue where the instance colour was not applied to the full name widgets (both user/community). It was previously using the name colour rather than the instance colour. This was found when I was working on #1281.

Issue Being Fixed

Issue Number: N/A

Screenshots / Recordings

Before

https://github.com/thunder-app/thunder/assets/30667958/9fe1d0d3-8946-4be2-bd73-1e5233a0cd46

After

https://github.com/thunder-app/thunder/assets/30667958/cd511605-9f24-4303-bcb9-a75ec475f8eb

Checklist

• [ ] Did you update CHANGELOG.md?
• [ ] Did you use localized strings where applicable?
• [ ] Did you add semanticLabels where applicable for accessibility?