Loose fancy blue diamonds are completely natural and are usually classified as either teal blue or ocean blue. The color in sea blue, teal blue diamond, turquoise blue, blackish blue or black blue colored diamonds is caused by the presence of minor amounts of boron in their structure. Green blue or greenish blue (teal) colored diamonds usually contain nitrogen impurities in aggregate form. Blue diamonds come in different intensity : Light Blue, Fancy Light Blue, Fancy Dark Blue, Fancy Deep Blue and Fancy vivid blue diamonds.