Are pink diamonds or yellow diamonds more expensive?
Natural pink diamonds are more rare than natural yellow
diamonds, probably because the common trace element nitrogen is
responsible for a yellow cast in a diamond. Some colourless or
'white' diamonds are considered yellow, when graded with a colour
grade from I to Z, as below.
Natural pink diamonds exist 'due to structural anomalies"
according to Wikipedia, and are very rare.
Some diamonds can be altered (or enhanced) to appear yellow or
pink, and when altered, are less valuable than naturally colored
diamonds.