The formation of yellow diamonds is due to increasing amounts of nitrogen atoms that were trapped inside the diamond's carbon atom structure during formation deep in the earth under high amounts of temperature and pressure.
With regard to color, natural yellow diamond ranges in color strength from nearly colorless (i.e., faint yellow), through pale wine yellow or butter yellow colors, gradually increasing in saturation up through various moderate shades of lemon yellow or daffodil yellow, and continuing in strength up through various vivid shades known as buttercup yellow and canary yellow.
The olive and gray color modifiers seen in natural yellow diamonds result from the impurities and the effect they have on light absorption in the visible spectrum. Brown and brownish are associated with structural defects that can occur with nitrogen impurities in a yellow diamond.
The Adamas Collection includes a beautiful flawless vivid yellow diamond as well as a round brilliant, burnt gold yellow diamond and a large cushion cut dominant yellow diamond that appears dominant green to the naked eye.