Colour - Refers to the degree to which
a diamond is colourless.
Colors range from very white to shades of many different
colors D being the highest color. View charts give a
better idea in the area of color for loose or certified
diamonds.

One this website you will see links to
JamesAllen.com
where you can purchase diamonds safely from the USA.
In the UK and Europe the diamond market is very highly
controlled to inflate profit margins to grossly unreasonable
levels. In the USA the markets are freer and you, the
customer, can make seriously huge savings. The UK jewellers
will tell you the diamonds are of less quality. That
is nonsense. Diamonds are certified for quality, so
don't be fooled! Buying a diamond from the USA will
give you a lot more diamond carat for your money! And
you know how important size is... ;)
Point to remember: Size and colour are immediately apparent.