But what is the problem? Natural (mined) Pink and Blue diamonds are much more expensive than their white counterparts - in the region of $100,000 to $250,000 per carat. If the subject diamond is 'coated' in the colour, surely the real value is almost the same as its donor diamond, after-all it is simply a coating? OK it may be a "diamond" coating but not through and through - just on the surface.
Our natural colour diamonds are not interfered with in any way, canary yellow is bright yellow and the 'Blues' range between Aqua and Sapphire.