A canary diamond is a bright yellow diamond. Though people think of a clear or white diamond when they think of a quality diamond, colored diamonds can be even more expensive.
Most diamonds that are considered colorless have a tinge of yellow in them due to the presence of nitrogen, but the color can't be seen with the naked eye. In yellow diamonds, nitrogen atoms group in very specific ways to produce color ranging from pale yellow to deep gold. After the color, the quality of the diamond is determined by how many flaws it has, how well it's cut and how large it is.