I grew out 5 Killing Fields (fem) and got 3 purple phenos and two green. Also had a coloured pheno from the Sugar Punch I've just been growing. Some autos I grew - super critical auto from greenhouse - also had coloured phenos, though these were nearer black than purple.
An outdoor Holland's Hope from Dutch Passion that my dad grew developed purple buds too. She was huge, 6ft+ and didn't finish properly due to cold temperatures, but the colours were insane.