The colous of titanium are caused by the reflection of the breaking light in the layer of oxidation.
The oxide itself has no pigment, it is colourless.
This fenomenon is called dispertion and is mostly known by everyone from the colours of oil on water. Oil and water are both transparent and together they cause this effect.
The layer of oxidation can be created by heat from a flame or in an oven. These ways are difficult to control though. A better way is to create the layer of oxidation by electrolisis.
The colours created depend on the thickness of the layer of oxidation.
Because the conductivity of the oxide is poor, the colour/thickness of the layer can be controlled by the voltage used.