Some systems include a dedicated channel for white ink whilst others require the use of an existing colour channel. It is not advisable to change colours once a machine has been configured as it is necessary to flush out the original colour, taking the system offline and wasting ink.
It is important to understand the costs of white ink printing. A comparatively large volume of white ink is required to create a white base layer and productivity can be reduced by as much as 50% if the printhead needs to make an additional pass.