octokit.net/docs/labels.md

Working with Issue Labels

Labels are appended using the method NewIssue.Labels.Add(x).

Example:

var myNewIssue = new NewIssue("Issue with dropdown menu");
myNewIssue.Labels.Add("bug");

The default labels that come with every repository are:

• bug
• duplicate
• enhancement
• help wanted
• invalid
• question
• wontfix

A Note on Label Colors

The official API returns colors without the leading # that you may expect when working with hex colors -- for example, white would return FFFFFF, not #FFFFFF.

If you're displaying the colors, you may need to add the # in order to display them properly.