How to print White registration marks (Printer with white ink only).
When printing on darker or black materials the default black registration marks are of no use or very limited use.
Problem:
With White printing active Caldera will print white underneath the black registration mark. In order to make the white visible one would have to assign a custom mark color. Use 1% Yellow to ensure that the marks will also be generated with the build in white generation options.

Under the White Tab enable the "Print Marks" option.
